Largest swings in percentage share of votes

Largest swings to an incumbent governing party

It is rare to see any swing towards the governing party in by-elections. However, there are some examples of it happening.

*BOLD indicates winning party

Largest fall in percentage share of vote

A party's share of the vote at a general election is not always matched at subsequent by-elections, but given the five-year maximum term of a Parliament, reductions of 20% or more are unusual. Those of 25% or more are listed below:

In the 1934 Merthyr by-election the Independent Labour Party share dropped from 69.4% in the 1931 general election to 9.8% (a record 59.6% loss) losing the seat to the Labour Party. However, the 1931 election had no Labour Party candidate, and the MP, R. C. Wallhead, had previously been elected as a Labour candidate in prior elections, when the ILP was affiliated to Labour. Prior to his death, Wallhead joined the Labour Party, so this result could be classed as a Labour hold.

The 1919 East Antrim by-election saw the Irish Unionist party face its first Unionist opposition in the seat since 1906 (in the 1918 general election the heavily unionist area gave the Irish Unionist 94.6% of the vote in a contest with a Sinn Féin candidate). An Independent Unionist candidate won the seat, with the Irish Unionist share dropping by 52.8%

Worst results for other parties:

Largest increase in percentage share of vote

Largest winning share of the vote

Winning shares of the vote above 90%, since 1918:

Largest numerical majority overturned

Majorities over 9,000 votes overturned:

Lowest winning share of the vote

Winning shares of the vote below 35%, since 1918:

The 1920 Stockport by-election, was held to elect two MPs. The winners' shares of the total vote were 25.6% and 25.1%. However, as each voter could cast two votes, the situation is not readily comparable to other by-elections in this period.

At the 1909 Sheffield Attercliffe by-election, the winning candidate took only 27.5% of the vote.

Lowest share of the vote

Smallest majorities

All majorities of less than 1,000 since the Second World War. Bold entries indicate a new record.

Still smaller majorities have been recorded since 1918. The majority in the 1921 Penrith and Cockermouth by-election, was only 31 votes, and in the 1924 Westminster Abbey by-election it was 43 votes, while at the 1928 Carmarthen by-election it was 47 votes.^[2] At the 1892 Cirencester by-election a majority of 3 for the Unionists was overturned on petition, where it was found that both candidates had an equal number of votes. A fresh by-election was called, which was won by the Liberals. The 1830 Liverpool by-election saw a majority of 29 votes.^[3]

Turnout

Turnout is the percentage of registered electors who voted.

Most candidates

Under current UK electoral law there is no upper or lower limit for candidature numbers, with the only required stipulation being the valid nomination of ten electors from the constituency. By-elections often attract "fringe" or novelty candidates, single-issue candidates, or independents. As with nominations in a general election, candidates must pay a £500 deposit, which is only refunded if the candidate wins 5% of the votes cast.

All by-elections with more than ten candidates are listed. Elections are listed in alphabetical order. Those that created a new record number appear in bold.

In 2017, the countermanded poll in Manchester Gorton had 11 candidates.

Fewest candidates

*¹ The most recent mainland UK instance only is given.

*² Four of these eight were between the Unionist incumbent and a "paper candidate" using the name "Peter Barry", the name of the then Irish Minister of Foreign Affairs.

Durable by-election candidates

Former MPs making a comeback at a by-election

Notes:

¹ by-election gain lost at the subsequent general election

² by-election gain held at the subsequent general election

Shortest-serving by-election victors

Note this list covers completed service only; it excludes any current MPs.

Youngest by-election victors

• Esmond Harmsworth, elected on 15 November 1919 from Isle of Thanet aged 21 years 170 days.^[8]
• Youngest woman: Bernadette Devlin, elected on 17 April 1969 from Mid Ulster aged 21 years 359 days.

Oldest by-election victors

Debuts in Parliament:

• John Benbow was 75 or 76 when he held the 1844 Dudley by-election for the Conservatives.
• Hucks Gibbs was 71 when he held the April 1891 City of London by-election for the Conservatives.
• Philip Manfield was 71 or 72 when he held the 1891 Northampton by-election for the Liberals.
• Sir Robert Pullar was 79 (less 6 days) when he held the 1907 Perth by-election for the Liberals.
• David Cleghorn Hogg was 73 when he gained the 1913 Londonderry City by-election for the Liberals.
• Sir Swire Smith was 73 when he held the 1915 Keighley by-election for the Liberals.
• William Frederick Hicks Beach was 74 when he held the 1916 Tewkesbury by-election for the Conservatives.
• Sir George Reid was 70 when he held the 1916 St George's, Hanover Square by-election for the Conservatives. He was a former Prime Minister of Australia.
• Sir John Fleming was 69 or 70 when he held the 1917 Aberdeen South by-election for the Liberals.
• George Edwards was almost 70 when he gained the 1920 South Norfolk by-election for Labour. He was a former agricultural labourer.
• Henry Bruce Armstrong was almost 77 when he held the 1921 Mid Armagh by-election for the Ulster Unionists.
• William Nathaniel Jones was 70 when he held the 1928 Carmarthen by-election for the Liberals.
• Francis Norie-Miller was 76 when he gained the 1935 Perth by-election for the Liberal Nationals.
• James Little was 70 when he held the 1939 Down by-election for the Ulster Unionists.
• John Evans was 70 when he held the 1946 Ogmore by-election for Labour.

Comebacks to Parliament:

• John Blaquiere was 71 when he held the June 1803 Downton by-election for the Tories. He was previously MP for Rye in 1801–02.
• Bartholomew Bouverie was 73 when he held the 1826 Downton by-election for the Tories. He was previously MP for the same seat from 1819 until the general election earlier in 1826.
• Quintin Dick was 71 when he held the 1848 Aylesbury by-election for the Conservatives. He was previously MP for Maldon in 1830–47.
• James William Freshfield was 77 when he won the 1851 Boston by-election for the Conservatives. He was previously MP for Penryn and Falmouth in 1835–41.
• William Johnson Fox was 71 when he held the 1857 Oldham by-election for the Liberals. He was previously MP for the same seat from 1852 until the general election earlier in 1857.
• William Cubitt was 71 when he held the 1862 Andover by-election for the Conservatives. He was previously MP for the same seat in 1847–61.
• John Morgan Cobbett was 71 when he won the 1872 Oldham by-election for the Conservatives. He had been previously MP for the same seat as a Liberal in 1852–65.
• James Patrick Mahon was 79 when he held the 1879 Clare by-election and 87 when he held the 1887 County Carlow by-election for the Irish Nationalists.
• Isaac Holden was 75 when he held the 1882 West Riding of Yorkshire by-election for the Liberals. He had previously been MP for Knaresborough in 1865–68.
• Sir Wilfrid Lawson was 74 when he held the 1903 Camborne by-election for the Liberals. He had previously been MP for Cockermouth in 1886–1900.
• John Frederick Cheetham was 70 when he won the 1905 Stalybridge by-election for the Liberals. He had served previously as MP for North Derbyshire 1880-85 prior to that seat's abolition.
• Sir Alfred Hopkinson was 74 when he won the 1926 Combined English Universities by-election for the Conservatives. He had previously been MP for Cricklade 1895-98 before resigning.
• Arthur Salter was 70 when he held the 1951 Ormskirk by-election for the Conservatives. He had served previously as MP for Oxford University 1937-50 prior to that seat's abolition.

In defence of a previously held seat:

• Enoch Powell was 73 when he successfully defended his seat at the 1986 South Down by-election for the Ulster Unionists, after a protest resignation against the Anglo-Irish Agreement, although he had been an MP almost continuously since 1950.

First women by-election victors

The first woman to be elected in a by-election was Nancy Astor, who succeeded her husband at the 1919 Plymouth Sutton by-election, becoming the first woman to take her seat in the House of Commons.

The first woman to gain a seat in a by-election was Susan Lawrence who won the 1926 East Ham North by-election, although she had previously sat for the same seat between 1923 and 1924.¹

The first woman to gain a seat ab initio in a by-election was Jennie Lee who won the 1929 North Lanarkshire by-election, at the same time becoming the first woman Baby of the House of Commons.

Note ¹ Mabel Philipson succeeded her husband at the 1923 Berwick-upon-Tweed by-election. He had been elected as a National Liberal Party candidate. She won as a Conservative so this could arguably be classed as the first gain by a woman.

First ethnic minority by-election victors

Whilst the first ethnic minority Members of Parliament were elected at general elections as early as the 1890s, it would be almost 100 years before one was returned at a by-election.

The first ethnic minority candidate to be elected in a by-election was Ashok Kumar who gained the 1991 Langbaurgh by-election for Labour.

• David Lammy held the 2000 Tottenham by-election for Labour.
• Mark Hendrick held the 2000 Preston by-election for Labour.
• Parmjit Singh Gill gained the 2004 Leicester South by-election for the Liberal Democrats.
• Seema Malhotra held the 2011 Feltham and Heston by-election for Labour, the first woman to win it.

The first by-election in which all three major-party candidates were from the ethnic minorities was the 2007 Ealing Southall by-election, held by Labour.

First by-election victors from specific religions

When the UK Parliament was established in 1801, non-Anglicans were prevented from taking their seats as MPs under the Test Act 1672. However, Methodists took communion at Anglican churches until 1795, and some continued to do so, and many Presbyterians were prepared to accept Anglican communion, thus ensuring that members of these creeds were represented in the Parliament.^[9] Some Unitarians were also elected.

The first by-election victor (and first ever MP) to be an adherent of the Eastern Orthodox Church was The Honourable Frederick North who was elected in 1792 for Banbury (to succeed his brother who had entered the House of Lords), having converted to the faith the previous year.

The first Roman Catholic by-election victor in the UK Parliament was Daniel O'Connell in the 1828 Clare by-election. He was not permitted to take his seat until the following year.

The first atheist by-election victor was Charles Bradlaugh, at the 1881 Northampton by-election. As an atheist, Bradlaugh was not allowed to swear the Oath of Allegiance, and the by-election was re-run in 1882 and 1884. Both were also won by Bradlaugh, who eventually was able to take his seat after the 1885 general election.^[10]

• David Salomons was the first Jewish by-election victor, at the 1851 Greenwich by-election.
• Terry Rooney was the first Mormon by-election victor, at the 1990 Bradford North by-election.
• Parmjit Singh Gill became the first Sikh by-election victor, at the 2004 Leicester South by-election.
• Virendra Sharma became the first Hindu by-election victor, at the 2007 Ealing Southall by-election.
• Rosena Allin-Khan was the first Muslim by-election victor, at the 2016 Tooting by-election.

Physically disabled by-election victors

Most physically disabled MPs in the history of the parliament entered in the intakes of general elections. Those known to have been disabled when entering parliament at by-elections are rarer and include:

• John Horne Tooke, who lost sight of an eye in a boyhood fight, won the 1801 Old Sarum by-election.
• Fulk Greville Howard, who lost sight of an eye in the Helder expedition in 1799, won the 1808 Castle Rising by-election.
• Sir William Carr Beresford, who lost sight of an eye in an accident on military service in 1786, won the 1811 County Waterford by-election.
• Samuel Shepherd, increasingly deaf from 1790, won the 1814 Dorchester by-election.
• Arthur MacMurrough Kavanagh, born without hands and feet, won the 1866 Wicklow County by-election.
• Michael Davitt, who lost his right arm in a factory accident in 1857, won the 1882 Meath by-election, although he was disqualified from sitting because he was in prison.
• Aubrey Herbert, who was almost blind from childhood, won the 1911 South Somerset by-election.
• Mabel Philipson, who lost sight in one eye after a car crash in 1911, who won the 1923 Berwick-upon-Tweed by-election.^[11][12]
• John Dugdale, who was partly deaf from childhood, won the 1941 West Bromwich by-election.
• Violet Bathurst, Lady Apsley, who was left permanently disabled and unable to walk by a hunting accident in 1930, won the 1943 Bristol Central by-election, ^[13]
• Cecil Manning, who lost his right arm in action in World War I, won the 1944 Camberwell North by-election.
• Hervey Rhodes, who walked with a limp since severe wounding in World War I, won the 1945 Ashton-under-Lyne by-election.
• William Rees-Davies, who lost his right arm in action in World War II, won the 1953 Isle of Thanet by-election.

By-elections losers awarded seats on disqualification of winner

• Malcolm St Clair, 1961 Bristol South East by-election (resigned in 1963 to enable another by-election)
• Charles Beattie, 1955 Mid Ulster by-election (he too was disqualified a few weeks later, causing another by-election)
• Pre-1945: Stephen Moore, March 1875 Tipperary by-election (retired in 1880)

Two or more former MPs contest by-election

• 2021 Hartlepool by-election¹ (three former MPs)
• 2008 Haltemprice and Howden by-election²
• 1997 Winchester by-election
• 1986 Fermanagh and South Tyrone by-election
• 1982 Beaconsfield by-election
• 1981 Warrington by-election
• 1969 Brighton Pavilion by-election
• 1965 Salisbury by-election
• 1956 Mid Ulster by-election
• 1948 Croydon North by-election
• 1933 Altrincham by-election (three former MPs)
• 1930 Glasgow Shettleston by-election
• 1930 Nottingham Central by-election (three former MPs)
• 1928 Cheltenham by-election

¹Hilton Dawson, Thelma Walker, and Paul Williams ² Conservative MPs David Davis and Walter Sweeney

Longest period without a by-election

The years 1998 and 2020 stand as the two in modern British history without any Westminster election. 1992, 1998, 2010 and 2020 are the four full calendar years in history without a single by-election.

Longest period between a vacancy arising and a by-election writ being moved

• 1941 The Wrekin by-election: 357 days. James Baldwin-Webb was presumed killed as a result of enemy action when SS City of Benares was torpedoed on 17 September 1940; the writ was moved on 9 September 1941.
• 1941 King's Norton by-election: 327 days. Ronald Cartland was killed in action on 29–30 May 1940. Initially posted missing, his death was not presumed until January 1941. The writ was moved on 22 April 1941.
• 1941 Hitchin by-election: 272 days. Sir Arnold Wilson was presumed killed in action on 31 May 1940; the writ was moved on 27 February 1941.
• 1969 Newcastle-under-Lyme by-election: 236 days. Stephen Swingler died on 19 February 1969; the writ was moved on 13 October 1969.
• 1969 Swindon by-election: 220 days. Francis Noel-Baker resigned on 7 March 1969; the writ was moved on 13 October 1969.

Longest period without a seat changing hands

The longest period without a seat changing hands in a by-election was the five years between the Conservative victories in the 1948 Glasgow Camlachie by-election and the 1953 Sunderland South by-election.

During the short Parliaments of 1910, 1950-1 and 1974 no seats changed hands in a by-election.

Longest period between by-election gains for a party

The Liberal Party endured 29 years without a single by-election gain between the 1929 Holland with Boston by-election and the 1958 Torrington by-election. It did not win a single by-election in the thirteen years between holding the 1945 Middlesbrough West by-election and gaining Torrington.

Until the 2008 Crewe and Nantwich by-election, the opposition Conservative Party had not gained a seat in almost 26 years, the last being the 1982 Mitcham and Morden by-election, which occurred during the unique circumstances of the Falklands War and the sitting Labour MP defecting to the Social Democratic Party and seeking re-election under his new party label. The Conservatives' last gain while in Opposition was 30 years previously at the 1978 Ilford North by-election.

Labour's longest lean stretch was almost 18 years, between gaining the 1939 Brecon and Radnorshire by-election and the 1957 Lewisham North by-election.¹

As of 17 January 2024, the most recent gains for each currently active party were:

Notes ¹ The Labour Party were the official opposition in the Parliament elected in 1935, but after the major parties agreed an electoral truce on the outbreak of war in 1939, they did not contest any Conservative or Liberal seats for the remainder of the Parliament, a period of six years, and were members of the wartime coalition government between May 1940 and May 1945.
² Notional gain: incumbent Conservative stood as UKIP. No UKIP candidate has ever defeated an incumbent of a different party
³ The UUP were also declared winners of the 1955 Mid Ulster by-election after the Sinn Féin candidate was disqualified, but the UUP candidate was also disqualified shortly after.
⁴ Sinn Féin have not gained a seat at a by-election since 1918. However, the Anti H-Block party, an Irish Republican group that merged into Sinn Féin, gained Fermanagh and South Tyrone in the April 1981 by-election (42 years, 9 months and 8 days ago).

Longest period between by-election holds for a party

The Conservatives did not successfully defend a single by-election in the eight years between their holds of the 1989 Richmond (Yorks) by-election and the 1997 Uxbridge by-election, losing a record 15 consecutive seats where they were the incumbents. By the time of the by-election in Uxbridge, the victor in Richmond, William Hague, had become leader of the Conservative Party.

Labour's worst run was 4 consecutive by-election losses, which has occurred three times since 1945:

• between holding the 1976 Newcastle-upon-Tyne Central by-election and the 1977 Grimsby by-election.
• between holding the 1967 Manchester Gorton by-election and the 1968 Sheffield Brightside by-election.
• between holding the 1967 Rhondda West by-election and the 1967 Manchester Gorton by-election.

Longest period between by-election losses for a party

Between the 1988 Glasgow Govan by-election and the 2003 Brent East by-election, Labour successfully defended every seat it held at by-elections, for a total of 30 holds (not counting Falkirk West and West Bromwich West, represented by a Labour MP turned independent and a Labour speaker respectively and both won by Labour). The span of 14 years, 10 months and 8 days is the longest period without a by-election defeat for either of the two main parties. The Conservatives did not lose a seat between the 2000 Romsey by-election and the 2012 Corby by-election, a span of 12 years, 6 months and 12 days. However, they only defended 3 seats in that time. In terms of total number, their longest run of by-election holds was 51, between the 1945 Chelmsford by-election and the 1957 Lewisham North by-election, a span of 11 years, 9 months and 21 days.

Since their formation, the Liberal Democrats have held every Lib Dem seat contested at a by-election, of which there have been 3. Including their successor parties, their most recent by-election loss was the 1982 Mitcham and Morden by-election, lost by the SDP 41 years, 7 months and 14 days ago. The SDP candidate had however defected from Labour – the last seat lost by either party that had been won at a previous election was the 1957 Carmarthen by-election, lost by the Liberals 66 years, 10 months and 20 days ago. Since 1982, the Liberal Democrats and predecessors together have defended 4; since 1957 they have defended 5 seats.

By-elections in seats held by minor and nationalist parties are rare, and so most have never lost a seat. The SNP lost their first seat at the 2023 Rutherglen and Hamilton West by-election. The DUP and Plaid Cymru have defended but never lost a seat at a by-election, Sinn Féin have only lost seats by disqualification, and the UUP have never lost more than one seat in a row. No by-election has ever been called in an SDLP held seat.

Longest period without an opposition gain

For a period of 11 years, from the 1997 general election until the 2008 Crewe and Nantwich by-election, the principal opposition Conservative Party failed to register a by-election gain against the incumbent Labour Government. This is the longest period of such failure since records began, and more than twice the previous record of the five years it took the then Labour opposition to gain the 1957 Lewisham North by-election. Labour did however lose 3 seats to the Liberal Democrats in that period, their first being the 2003 Brent East by-election.

The present Labour opposition did not register a gain for over nine years, between the 2012 Corby by-election and the 2022 Wakefield by-election. In this period, the Conservative government lost three seats in by-elections where the former Conservative incumbent stood for a different party (2014 Clacton by-election and 2014 Rochester and Strood by-election, both lost to UKIP) or as an independent (2016 Richmond Park by-election, lost to the Liberal Democrats). Their first loss in a by-election without a sitting incumbent was to the Liberal Democrats at the 2019 Brecon and Radnorshire by-election.

Apart from the brief parliaments of 1910, 1950-1 and 1974, the parliaments of 1951-5 and 1997-2001 are the only occasions when the Government did not lose a by-election.

Most by-elections in one day

The largest number of by-elections held on a single day occurred on 23 January 1986 when 15 simultaneous contests were held in Northern Ireland. The elections had been engineered by the incumbent Unionist parties as a protest against the Anglo-Irish Agreement of 1985. They intended the results to be interpreted as a referendum on the treaty. The elections were boycotted by the main Nationalist parties except in four seats where they had a reasonable prospect of victory. In the event, the Social Democratic and Labour Party gained one seat, Newry and Armagh, from the Ulster Unionist Party.

Apart from the above example, it is common for UK mainland parties to schedule several by-elections on the same day. Motivations include attempting to divide opponents' resources and getting bad news (expected losses) out of the way. Since 1945, the largest number of simultaneous mainland by-elections has been 6, held on 16 November 1960. On four occasions, 5 by-elections have been held on the same day, most recently on 9 June 1994. Groupings of two or three are very common.

Before November 2012, the last day on which three by-elections had been held was 23 November 2000. In November 2012 there were two such groupings of three (15 November and 29 November). The last time there were six by-elections in one calendar month was in June 1994.

Most by-election losses in one day

The largest number of by-elections lost on a single day is three, when the Labour party lost Acton, Dudley and Meriden on 28 March 1968, all to the Conservatives.

Occasions since 1945 when two seats have fallen are:

Seats with more than one by-election in a single Parliament

• Bootle: May and November 1990.
• Fermanagh and South Tyrone: April and August 1981.
• Bristol South East: 1961 and 1963.
• Mid Ulster: 1955 and 1956.
• Edinburgh East: 1945 and 1947.
• Middlesbrough West: 1940 and 1945.
• Combined Scottish Universities: 1936, 1938 and 1945.
• Berwick-upon-Tweed: 1941 and 1944.
• Clay Cross: 1936 and 1944.
• West Derbyshire: 1938 and 1944.
• Buckingham: 1937 and 1943.
• Manchester Gorton: 1937 and 1942.
• Dunbartonshire: 1936 and 1941.
• Greenock: 1936 and 1941.
• Doncaster: 1938 and 1941.
• Southampton: February and November 1940.
• Preston: 1936 and 1940.
• Wandsworth Central: 1937 and 1940.
• City of London: 1938 and 1940.
• Combined Scottish Universities: 1934 and 1935.
• Eastbourne: 1932 and 1935.
• Twickenham: 1932 and 1934.
• Portsmouth South: 1922 and 1923.
• North Down: 1921, February and July 1922.
• West Down: 1921 and 1922.
• South Londonderry: 1921 and 1922.
• Louth: 1920 and 1921.
• The Wrekin: February and November 1920.
• North Londonderry: 1919 and 1922.
• Prestwich: January and October 1918.
• Edinburgh and St Andrews Universities: 1916 and 1917.
• St George's Hanover Square: 1913, 1916 and 1918.
• City of London: February and June 1906.
• Oswestry: 1901 and 1904.
• Southport: 1898 and 1899.
• City of London: April and June 1891.
• Buckingham: 1889 and 1891.
• Ayr Burghs: 1888 and 1890.
• Northampton: 1881, 1882 and 1884.
• Preston: 1881 and February and November 1882.
• Bath: May, June and October 1873.
• South Shropshire: 1866 and 1867.
• East Gloucestershire: January and December 1854.
• Greenwich: 1851 and 1852.
• South Nottinghamshire: 1848 and 1852.
• Buckinghamshire: 1837 and 1839 and 1842 and 1845, within two successive parliaments.

By-election days

British Parliamentary elections are invariably held on a Thursday. The last by-election not held on a Thursday was the 1978 Hamilton by-election, held on Wednesday 31 May due to a World Cup opening match on the Thursday evening.

Due to an administrative oversight, the 1973 Manchester Exchange by-election was held on Wednesday 27 June 1973. Prior to that, the last by-elections not held on a Thursday were the 1965 Saffron Walden by-election held on Tuesday 23 March, and the 1965 Roxburgh, Selkirk and Peebles by-election held the following day.

Until the mid-1960s, it was common to hold by-elections on any day of the week (other than Sunday).

Countermanded poll

Very occasionally, a scheduled by-election may be overtaken by the calling of a general election and the dissolution of Parliament, in which case the poll is countermanded by the Returning Officer. There have been only three occasions since 1918: a by-election was scheduled to take place in Warwick and Leamington on 21 November 1923, but was cancelled by a dissolution of Parliament on 16 November. A by-election was scheduled to poll between 13 and 17 October 1924 in London University but was cancelled by a dissolution of Parliament on 9 October. In 2017 the Manchester Gorton by-election was cancelled by a Motion in the House of Commons following the calling of the 2017 United Kingdom general election.^[14]

Seats left vacant

Occasionally seats are left vacant for a substantial period.

No by-election writ was moved for any seat held by Sinn Féin after the 1918 general election. Four Sinn Féin candidates were elected in two different seats and would have had to decline one of them if they had wanted to take their seats. They were Éamon de Valera (East Clare and East Mayo), Arthur Griffith (East Cavan and North West Tyrone), Eoin MacNeill (Londonderry City and National University of Ireland) and Liam Mellowes (East Galway and North Meath).

By the end of the Parliament, the following Sinn Féin MPs had died without being replaced: Pierce McCan (East Tipperary) of influenza on 6 March 1919, Terence MacSwiney (Mid Cork) following a hunger strike in Brixton prison on 25 October 1920, Frank Lawless (North Dublin) as a result of a riding injury on 16 April 1922, Joseph McGuinness (Longford) on 31 May 1922, Cathal Brugha (Waterford) in action during the Irish Civil War on 7 July 1922, Harry Boland (South Roscommon) shot while being arrested on 2 August 1922, Arthur Griffith (East Cavan and North West Tyrone) on 12 August 1922, and Michael Collins (South Cork assassinated on 22 August 1922). In each case their seats were abolished in 1922 as a result of the establishment of the Irish Free State.

Other than these cases the longest time a seat has been left vacant with no by-election held is when Dennis Vosper was elevated to the Peerage on 20 April 1964, and no writ was moved by the time Parliament was dissolved on 25 September 1964.

By-elections prompted by assassination

By-elections prompted by suicide

Note

¹Death by hunger strike.

By-elections prompted by accidental death

By-elections prompted by posthumous election of MP

• 1945 Bromley by-election: Sir Edward Taswell Campbell died before his election declaration at the 1945 general election.
• 1945 Monmouth by-election: Leslie Pym died before his election declaration at the 1945 general election.
• 1935 Combined Scottish Universities by-election: Noel Skelton died before his election declaration at the 1935 general election.
• 1906 North Galway by-election: Thomas Higgins died before his election declaration at the 1906 general election.

By-elections prompted by scandal

• 2023 Tamworth by-election: Chris Pincher resigned, after losing an appeal against suspension from the House of Commons, in the wake of allegations that he had drunkenly groped two men. The Committee for Standards concluded Pincher's "profoundly damaging" behaviour "represented an abuse of power", causing significant damage to Parliament's reputation. The scandal was also instrumental in the fall of Prime Minister Boris Johnson.
• 2023 Rutherglen and Hamilton West by-election: the seat was declared vacant after Margaret Ferrier lost a recall petition, after Ferrier was convicted at Glasgow Sheriff Court of breaching COVID-19 travel rules in 2020, and suspended from the House of Commons.^[20]
• 2023 Somerton and Frome by-election: David Warburton resigned in advance of results of investigation into alleged sexual harassment, and his admission to taking cocaine.^[21]
• 2023 Uxbridge and South Ruislip by-election: Former Prime Minister Boris Johnson resigned 'with immediate effect', in advance of findings of his repeated contempts, and that he deliberately misled Parliament over Partygate, warranting a 90-day suspension.^[22]
• 2022 City of Chester by-election: Chris Matheson resigned after being suspended for serious sexual misconduct.^[23]
• 2022 Tiverton and Honiton by-election: Neil Parish resigned after admitting watching pornography in the House of Commons.
• 2022 Wakefield by-election: Imran Ahmad Khan resigned after his conviction of sexual assault on a 15-year-old boy.
• 2021 North Shropshire by-election: Owen Paterson resigned amid controversy surrounding a report by the Parliamentary Commissioner for Standards that found that him broken paid advocacy rules.
• 2021 Hartlepool by-election: Mike Hill resigned in advance of an employment tribunal verdict that he had assaulted, harassed and victimised a parliamentary worker.
• 2019 Brecon and Radnorshire by-election: the seat was declared vacant after Chris Davies pleaded guilty to filing false expenses claims, and a recall petition was successful.
• 2019 Peterborough by-election: the seat was declared vacant after Fiona Onasanya was convicted of perverting the course of justice in relation to motoring penalty points issued in 2017. This was the first successful recall petition under the provisions of the Recall of MPs Act 2015.
• 2018 West Tyrone by-election: Barry McElduff resigned after becoming embroiled in a social media controversy.
• 2014 Newark by-election: Patrick Mercer resigned after being suspended from the House of Commons for six months by the Parliamentary Standards Committee for asking parliamentary questions in exchange for money.
• 2013 Eastleigh by-election: Chris Huhne resigned after pleading guilty to perverting the course of justice in relation to persuading his wife to accept motoring penalty points in 2003.
• 2012 Rotherham by-election: Denis MacShane resigned after House of Commons Standards and Privileges Committee recommended he be suspended from the service of the House for twelve months; their inquiry arose from the United Kingdom Parliamentary expenses scandal.
• 2011 Barnsley Central by-election: Eric Illsley resigned after pleading guilty to charges of false accounting arising from the United Kingdom Parliamentary expenses scandal.
• 2009 Glasgow North East by-election: Michael Martin resigned as Speaker rather than face a vote of no confidence, amid criticism of his actions arising from the United Kingdom Parliamentary expenses scandal.
• 2009 Norwich North by-election: Ian Gibson resigned after being debarred as a Labour candidate, due to allegations arising from the United Kingdom Parliamentary expenses scandal.
• 1997 Beckenham by-election: Piers Merchant resigned after a newspaper story revealed that his previous denials of an affair were lies.
• 1977 Bournemouth East by-election: John Cordle resigned after he was criticised by a Select Committee for business links to corrupt architect John Poulson.
• 1976 Walsall North by-election: John Stonehouse resigned after being convicted of insurance fraud.
• 1973 Berwick-upon-Tweed by-election: Antony Lambton resigned after his visits to prostitutes and use of cannabis were exposed by the News of the World.
• 1963 Stratford-upon-Avon by-election: John Profumo resigned after his denials of an affair with Christine Keeler were shown to be lies.
• 1959 Harrow East by-election: Ian Harvey resigned after conviction for gross indecency with a guardsman in Hyde Park.
• 1953 Paddington North by-election: Bill Field resigned after conviction for importuning for immoral purposes in a public lavatory.
• 1949 Sowerby by-election: John Belcher resigned after being found to have accepted gifts from businessmen for political favours.
• 1941 Scarborough and Whitby by-election: Sir Paul Latham resigned after he was arrested to be tried by court-martial on 13 charges of disgraceful conduct.
• 1936 Derby by-election: James Henry Thomas resigned after being found to have disclosed budget secrets.
• 1936 Balham and Tooting by-election: Sir Alfred Butt resigned after being found to have disclosed budget secrets.
• 1931 Pontypridd by-election: Thomas Mardy Jones resigned after being found to have abused a travel voucher.
• 1926 Buckrose by-election: Guy Gaunt resigned after being cited as co-respondent in a divorce case.

By-elections prompted to provide seat for seat-less personality

• 1965 Nuneaton by-election: For Frank Cousins.
• 1965 Leyton by-election: For Patrick Gordon Walker (defeated).
• 1950 Sheffield Neepsend by-election: For Frank Soskice.
• February 1940 Southampton by-election: For Sir John Reith.
• 1940 Wandsworth Central by-election: For Ernest Bevin.
• 1922 Portsmouth South by-election: For Leslie Orme Wilson.
• February 1906 City of London by-election: For Arthur Balfour.
• 1896 Montrose Burghs by-election: For John Morley.

By-elections prompted by party disputes and defections

By-elections are ostensibly to vote for a 'person', not a 'party', meaning that a member switching parties mid-term is not cause for a by-election. However, some members do seek re-election under their new party as a point of principle.

By-elections resulting from Members resigning on principle

• 2024 Kingswood by-election: Chris Skidmore resigned in opposition to a bill that allows the issuance of new oil and gas licences.
• 2016 Richmond Park by-election: Zac Goldsmith resigned to force a by-election on the issue of the expansion of Heathrow Airport, and contested as an Independent. He was defeated by Sarah Olney of the Liberal Democrats. Goldsmith later regained his seat the following year at the 2017 general election.
• 2008 Haltemprice and Howden by-election: David Davis resigned to force a by-election on the issue of civil liberties. He was re-elected with neither of the other main parties contesting the seat.
• 1986 Northern Ireland by-elections: Fifteen Unionist MPs resigned and re-contested their seats in protest at the Anglo-Irish Agreement. All but one was re-elected.
• 1963 Bristol South East by-election: Malcolm St Clair honoured a pledge to stand down if law changed to allow Tony Benn to disclaim his peerage.
• 1938 Kinross-shire and Perthshire by-election: The Duchess of Atholl resigned in protest at Neville Chamberlain's appeasement policy and sought re-election. She was defeated.
• 1927 Southwark North by-election: Leslie Haden-Guest resigned from the Labour Party over its policy on China, and re-contested the seat as an Independent Constitutionalist with Conservative support. He was defeated, finishing bottom of the poll. The Liberals gained the seat.
• 1927 Leith by-election: William Wedgwood Benn resigned following his resignation from the Liberal party and joining the Labour Party. He did not contest the by-election out of fairness to the existing Labour candidate. The seat was narrowly held by a new Liberal candidate.
• 1914 Cork City by-election: William O'Brien resigned to submit himself to the voters after the Irish Nationalists had made council gains in Cork. He was returned unopposed.
• 1912 Bow and Bromley by-election: George Lansbury resigned to contest his seat on the issue of Women's Suffrage, although he was disenchanted with a range of Labour party policies. He was defeated.
• 1909 Stratford-on-Avon by-election: Thomas Kincaid-Smith resigned from the Liberal Party on the issue of compulsory national service. He stood as an Independent with National Service League support. He was defeated, finishing bottom of the poll.
• 1906 Mid Cork by-election: D. D. Sheehan resigned and re-contested his seat following his expulsion from the Irish Nationalist group for not signing the party pledge. Re-elected as an independent.

By-elections prompted by Member's desire to contest another seat

• 1918 East Tyrone by-election: William Redmond resigned in order to defend his late father's seat at Waterford City. He was successful.
• 1914 East Worcestershire by-election: Austen Chamberlain resigned in order to defend his late father's seat at Birmingham West. He was successful.
• 1911 East Wicklow by-election: John Muldoon resigned in order to contest the East Cork by-election. He was successful.

By-elections caused by the previous result being declared void

• 2011 Oldham East and Saddleworth by-election: The result of the 2010 general election was declared void because the victor was found guilty of knowingly making false statements about a rival candidate.
• 1997 Winchester by-election: The result of the 1997 general election was declared void because ballot papers which had not received the official mark would have affected the result, if counted. Liberal Democrat Mark Oaten massively increased the minute majority he had achieved in the general election.
• 1924 Oxford by-election: The result of the 1923 general election was declared void because there were irregularities in the election expenses of the successful candidate.
• 1923 Berwick-upon-Tweed by-election: The result of the 1922 general election was declared void because there were irregularities in the election expenses of the successful candidate.
• 1911 North Louth by-election: The result of the December 1910 general election was declared void because of corrupt practices and bribery on the part of the successful candidate.

By-elections prompted by disqualification of the sitting Member

• 1961 Bristol South East by-election: Tony Benn had inherited a Peerage from his father. Although by-elections were routinely called where Members had succeeded to the Peerage, the seat was not considered vacated until the Member had received a Writ of Summons to the House of Lords, and Benn, who refused to accept the Peerage, did not apply for one. The seat was declared vacant by a resolution of the House of Commons.
• 1956 Mid Ulster by-election: Charles Beattie was found to be disqualified through membership of National Assistance panels. A bill indemnifying him from the consequences of acting as an MP while disqualified was passed by the House of Commons; Beattie did not stand in the by-election.
• 1955 Mid Ulster by-election: Tom Mitchell was disqualified as a felon (resolution of the House).
• 1950 Belfast West by-election: Rev James Godfrey MacManaway was found by the Judicial Committee of the Privy Council to be disqualified, as a Minister of the Church of Ireland.
• 1925 Walsall by-election: William Preston was found to be disqualified owing to his holding government contracts. A bill indemnifying him was passed by the House of Commons and Preston was re-elected at the by-election.
• 1924 Dover by-election: John Astor was disqualified for voting before he took the oath. He was returned unopposed at the by-election.
• 1913 Whitechapel by-election: Sir Stuart Samuel was found to be disqualified owing to his holding government contracts. A bill indemnifying him was passed by the House of Commons and Samuel was narrowly re-elected at the by-election.
• 1904 City of London by-election: Alban Gibbs was found to be disqualified owing to his holding government contracts. Gibbs resigned and was re-elected unopposed at the by-election.
• 1904 St Albans by-election: Vicary Gibbs was found to be disqualified owing to his holding government contracts. Gibbs resigned and was narrowly defeated at the by-election.

By-elections prompted by expulsion from the House

• 1955 South Norfolk by-election: Peter Baker was expelled after being convicted of uttering forged documents.
• 1947 Gravesend by-election: Garry Allighan was expelled after being found to be in extreme contempt of the House by his peers after selling details of private parliamentary meetings to the Evening Standard.
• 1922 Hackney South by-election: Horatio Bottomley was expelled after being convicted of fraud, perjury and false accounting.
• 1903 Galway Borough by-election: the seat was declared vacant after Arthur Alfred Lynch was convicted of high treason after fighting on the Boer side in the Second Boer War.

By-elections prompted by lunacy

• 1916 Colne Valley by-election: Charles Leach was adjudged a lunatic and his seat declared vacant.

By-elections prompted by bankruptcy

• 1928 Ashton-under-Lyne by-election: Cornelius Homan lost his seat after being declared bankrupt.
• 1922 Camberwell North by-election: Henry Newton Knights lost his seat after being declared bankrupt.
• 1914 North Galway by-election: Richard Hazleton resigned before being declared bankrupt. He discharged his bankruptcy and was returned in the by-election.
• 1912 Hackney South by-election: Horatio Bottomley resigned after filing a bankruptcy petition.
• 1909 South Kilkenny by-election: Nicholas Joseph Murphy was declared bankrupt.

By-elections prompted for miscellaneous reasons

• 1916 Widnes by-election: William Hall Walker resigned to permit him to donate his thoroughbred racing stock to create a National Stud in an "arms-length" transaction. He was returned unopposed at the by-election.

By-elections prompted by death of member on wartime active service

Incumbents fall directly from first place to third place

• 1995 Littleborough and Saddleworth by-election Conservative loss, gained by the Liberal Democrats
• 1995 Perth and Kinross by-election Conservative loss, gained by the SNP
• 1994 Eastleigh by-election Conservative loss, gained by the Liberal Democrats
• 1985 Brecon and Radnor by-election Conservative loss, gained by the Liberals
• 1982 Mitcham and Morden by-election¹ Labour loss, gained by the Conservatives
• 1958 Rochdale by-election Conservative loss, gained by Labour
• 1934 Merthyr by-election ILP loss, gained by Labour
• 1929 Holland with Boston by-election Conservative loss, gained by the Liberals
• 1927 Bosworth by-election Conservative loss, gained by the Liberals
• 1926 Kingston upon Hull Central by-election² Liberal loss, gained by Labour
• 1920 South Norfolk by-election Liberal loss, gained by Labour

¹ Bruce Douglas-Mann had been re-elected as Labour MP for the seat in the 1979 general election. In 1981, along with several other MPs, he defected to the newly formed Social Democratic Party. Against his new colleagues' advice, he honoured a pledge to face his electors under his new party colours and precipitated a by-election. He came second in the by-election which was won by the Conservatives. The new Labour candidate finished third.

² the Liberal MP, Lt-Commander the Hon. Joseph Montague Kenworthy, defected to Labour and sought re-election under his new colours. He was successful, and the new Liberal candidate lost his deposit.

Incumbent government gains seats

These records show the rare occasions when the government won a seat they had not won at the previous general election.

Principal Opposition loses seats

These records show the rare occasions when the official Opposition failed to hold on to a seat they had won at the previous General election.

¹A confused situation, where the victorious Empire Free Trade Crusade candidate was effectively a right-wing unofficial Conservative, who subsequently took the whip and was re-elected as official Conservative candidate.

²seat awarded by Election Court to Conservative runner-up because Labour victor Viscount Stansgate was deemed ineligible.

³Sir Owen Thomas had been elected as Independent Labour, took the whip for a while, before reverting to Independent Labour.

⁴Lost to Coalition Conservatives (see Coalition Coupon)

By-election holds overturned at next general election

On rare occasions a party has failed to overturn an incumbent in the by-election yet has gone on to gain the seat at the subsequent general election.

By-election victors had not contested previous general election

It is unusual for a political party which has not contested a seat at a general election to take it at a subsequent by-election. Independent candidates are not included.

Notes:

¹ Alliance partner the Liberal party had contested the seat.

² The victor was the sitting MP, who had left the Labour party.

³ Candidate endorsed by the coalition government.

⁴ The victor was the sitting MP, who had left the Conservative party.

Additional victories by minor parties

In addition to the above section, other minor party successes include the following. For a complete list, see the list of UK minor party and independent MPs elected.