
By-Elections often appear to be like buses, you don’t have one for ages and then a number arrive at once. The five by-elections that took place between July and October 2023 seem indicative of this. So, what is a by-election, why might one take place and how significant are they?
What is a by-election and in what circumstances will they be held?
A by-election is an election called when a seat has been vacated within a constituency, but there is no General Election looming. In the United States these are called Special Elections. In the UK there are four main circumstances in which a by-election will be held:
- If an MP dies

The average age of MPs elected at the 2019 General Election was 51 whilst 21 MPs elected were over the age of 70. With 650 MPs in total, it is not surprising that sometimes a vacancy emerges because of the death of an MP. At the time of writing the last MP to pass away in office was Jack Dromey, the widely respected Labour MP.
Most MPs who do die in office do so of natural causes. However, unfortunately some have been murdered, including:

Sir David Amess – In 2021 David Amess, the MP for Southend West, was murdered during one his constituency surgeries. In April 2022 his killer, Ali Harbi Ali, was sentenced to life imprisonment.
Jo Cox – Jo Cox was murdered in June 2016 by a far-right extremist in a senseless attack. The tributes paid to Jo Cox from every corner of the House of Commons left no doubt that she was seen as a highly dedicated and courageous Member of Parliament.
Ian Gow – Ian Gow was killed by a car bomb placed under his car by the Provisional IRA. The Provisional IRA claimed the responsibility for the attack and said that Gow had been targeted due to his close relationship with Margaret Thatcher.

Airey Neave – Like Gow, Conservative MP Airey Neave was killed by a car bomb. In this case, responsibility was claimed by the Irish National Liberation Army. Neave had been Shadow Secretary of State for Northern Ireland and believed that the IRA had to be faced head on by the British Government. In the case of Neave, no by-election was needed as he died in March 1979 but a General Election was scheduled for May 1979. His seat was comfortably won by the Conservatives.

In the case of both Sir David Amess and Jo Cox, the major parties agreed not to stand in the following by-elections to ensure that the seat was won by the parties that already held it, something that would at least honour the wishes of the deceased.
2. If an MP Resigns

When most MPs resign they decide to stay in their seat until the next General Election. There is no job description for an MP so they can essentially ‘take it easy’ until the election arrives. For example, after Gordon Brown lost the 2010 General Election he remained as a Labour MP. However, he was extremely inactive during this period, rarely attending or speaking in debates. In the whole Parliament he only voted in 152 of 1239 votes, 12.3% of the total. However, some MPs do step down immediately. For example, Labour MP Tristram Hunt resigned in January 2017 in order to become Director of the Victoria and Albert Museum.
Interestingly, MPs do not ever technically resign. This is because to do so would be an affront to the King. They are therefore given the honorary title of Steward of the Chiltern Hundreds or Crown Steward of the Manor of Northstead. Traditionally, both of these were a paid title from the monarch that would preclude someone from being an MP. Therefore, being ‘promoted’ to Steward of the Chiltern Hundreds or Steward of the Manor of Northstead allowed an MP to resign without offending the monarch.


3. Due to a term of imprisonment for over one year

Any sitting MP who is imprisoned for a period of more than one year is automatically disbarred from the House of Commons and therefore vacates their seat. This has only happened twice since 1945:
Peter Baker (Conservative) – Imprisoned for forgery in 1954.
John Stonehouse (Labour) – Imprisoned for seven years for fraud.
4. Due to a successful recall petition under the Recall of MPs Act (2015)
Until 2015 death, resignation and imprisonment of over one year were the only circumstances under which an MP could be removed. However, Recall of MPs Act (2015) extended that list through a new constitutional mechanism. A recall petition can be initiated if any of the following three criteria are met:
- An MP is imprisoned for less than a year (imprisonment of more than year automatically disqualifies MPs from sitting in the House of Commons).
- An MP is suspended from the House of Commons for 10 or more sitting days or 14 or more calendar days.
- An MP is convicted for providing false expenses claims.
As of October 2023 three by-elections have been held due to successful recall petitions under the Act:

Labour MP Fiona Onasanya was imprisoned for perverting the course of justice. A total of 28% of her constituents signed the recall petition (10% is needed to force a by-election). Onasanya did not stand in the resultant by-election which was narrowly won by Labour’s Lisa Forbes.

Conservative MP Christopher Davies was convicted for providing false expenses claims. A total of (18.9%) of his constituents voted to trigger a by-election. Davies decided to stand in the resultant by-election and, bizarrely, was even selected to be the Conservative candidate. The Liberal Democrats won the by-election with Jane Dodds becoming the MP (although she lost her seat just four months later in the 2019 General Election).
Former SNP MP Margaret Ferrier was removed following a recall petition over her failure to follow COVID-19 protocols. In September 2020 Margaret Ferrier had symptoms of COVID-19. She took a COVID test but whilst awaiting for the results she went to a number of public places and also took a train from London to Scotland. Her failure to isolate was a clear breach of the COVID regulations at that time.
What impacts how significant by-elections are?
The significance of each by-election will depend based on a number of factors. Some of the factors that will impact their importance are:
- The current parliamentary arithmetic

If a government has only a small parliamentary majority then every seat becomes increasingly important. If a government has a firm majority, the result will not matter as much. An example of this occurred with James Callaghan’s Labour Government. After the October 1974 election Labour formed a minority government. However, during the Parliament Labour lost a number of seats in by-elections. This meant that when Callaghan became PM in 1976 his position was very precarious. In 1979 Callaghan lost a motion of no confidence, leading to a General Election after which the Conservatives took power for 18 years. Callaghan lost this motion by a single vote. Notably, in 1977 and 1978 there were three by-elections that saw Conservative gains from Labour. These changed the parliamentary arithmetic enough to eventually bring down the government.
- The majority in the constituency
If the seat is a safe seat for the government it is going to be seen as less important as they are almost certain to win it. However, if the seat is a marginal seat, the focus on the by-election may be greater as it is more likely to give a sense of what might happen at the next general election and it might well change as a result of the by-election. It should be noted however, that sometimes political circumstances mean that even safe seats may change at a by-election. There have been some very significant majorities overturned in recent by-elections, in particular achieved by the Liberal Democrats:
2023 Somerton and Frome – This saw a swing of 29.0% as the Liberal Democrats took the seat from the Conservatives who previously had a majority of 19,213.
2022 Tiverton and Honiton – This saw a swing of 29.9% as the Liberal Democrats took the seat from the Conservatives who previously had a majority of 24,239.
2021 North Shropshire – This saw a swing of 34.2% as the Liberal Democrats took the seat from the Conservatives who previously had a majority of 22,949.
2021 Chesham and Amersham – This saw a swing of 25.2% as the Liberal Democrats took the seat from the Conservatives who previously had a majority of 16,223.
- The current political circumstances and the timing of the by-election

The current political circumstances and the by-election can have a big impact on its significance. If a government is in trouble, a by-election loss can heap more pressure onto them. In addition, a by-election can bring an issue into political focus. In July 2023 it was widely expected that in the by-election following the resignation of Boris Johnson his Uxbridge and South Ruislip constituency might fall to Labour. However, the by-election appeared to be less about the record of Boris Johnson and more a referendum on the decision of the Labour mayor of London, Sadiq Khan, to extend the ULEZ zone. The Conservative candidate, Steve Tuckwell, was consequently able to cling onto the seat for the party.
- Why the election is being held
The causes behind the by-election may have a significant impact on how the vote goes. For example, if an MP has resigned in disgrace, this may have an impact on whether the incumbent party is able to retain the seat. For example, the Selby and Ainsty by-election too place after Nigel Adams suddenly resigned following the resignation of Boris Johnson. There was a sense in the constituency that he had abandoned his duties and this undoubtedly helped Labour to take the seat.
Why might by-elections sometimes be very significant?
One of the particular problems with by-elections is that they often have low turnout compared to General Elections. In some ways this is surprising, as national focus is placed on the area in question. However, the hype created by the run-up to a General Elections is missing and this often produces lower turnout. For example, the 2012 Manchester Central By-Election had turnout of just 18.2%.
Despite generally lower turnouts, there are ways in which by-elections can be very significant:
- They provide a showcase for smaller parties.
By-Elections provide the national focus that minor parties crave. During a by-election national attention is focused on the constituency. Whilst minor parties are still unlikely to win the by-election, they can get higher than normal media coverage through them. By-Elections normally see far more candidates than a normal election would see in the constituency. The highest number of candidates in a by-election was an incredible 26 in the 2008 by-election in Haltemprice and Howden.

By-Elections can often see relative success for extremist parties. For example, in the 2011 by-election in Barnsley Central and 2012 Rotherham by-election saw the British National Party (BNP) finish in 3rd and 4th position.
2. They often become mini-referendums on a particular issue.
At times, by-elections can become referendums on the dominant political issue of the day. Notably, between 2016 and 2019 Brexit was a dominant issue in by-elections. However, often by-elections are dominated by local or more niche issues:

1983 Bermondsey – The by-election in Bermondsey in 1983 became dominated by the issue of homosexuality. The Labour candidate, Peter Tatchell, was homosexual. Although the Labour Party urged him to keep quiet about this, it became a major issue in the campaign and he was attacked by his fellow candidates in a horrific campaign. The winning Liberal Party seemingly joined in with the homophobic attacks, with some male campaigners wearing a badge saying “I’ve been kissed by Peter Tatchell”. Tatchell was emphatically defeated, despite it being previously a very safe Labour seat in the 1979 election. Britain was a far more socially conservative country in 1983 than it is today, and it showed in the election result.
2008 Haltemprice and Howden – Conservative MP David Davies resigned in order to force a by-election in 2008. He resigned in protest at what he perceived to be the erosion of civil liberties in the UK. The by-election saw a record 26 candidates, even though both the Labour Party and Liberal Democrats refused to put forward a candidate (Labour called it a farce, whilst the Lib Dems said they supported Davis’ stance on civil liberties). Davies comfortably won the by-election, with many of the debates surrounding issues of civil liberty.

2016 Richmond Park – This by-election was caused by Conservative MP Zac Goldsmith resigning. He was resigning as an MP in protest at the government’s decision to build a third runway at Heathrow. He ran in the by-election as an independent candidate and hoped to be elected and send a clear message to the government over its plans for Heathrow. Despite Goldsmith’s plans, the by-election became a mini-referendum on Brexit, which was by far the dominant issue in the resulting campaign. Even though the Conservatives did not put up a candidate against Goldsmith, the election was won by Liberal Democrat Sarah Olney.
3. They are often a reflection on the current government.
Governments tend to perform extremely poorly in by-elections. By-Elections often become a referendum on the performance of the party in government. However, they are also harder for the governing party to win than General Elections as they are not really able to put forward a raft of new policies. Notably, between 1982 and 2017 the governing party made no gains (winning seats they did not hold previously) at by-elections.
What has the result been in recent by-elections?
Somerton and From (July 2023)
Reason for By-Election: The resignation of David Warburton, 14 months after he had been suspended by the Conservative Party for allegations he had sexually harassed three women.
Previous Majority: 19,213 (Conservative)
Result: The Liberal Democrat Sarah Dyke won the seat with a 29% swing.
Selby and Ainsty (July 2023)
Reason for By-Election: The sudden resignation of Nigel Adams.
Previous Majority: 20,137 (Conservative)
Result: The Labour candidate Keir Mathers won the seat. Mathers, aged just 25, therefore became the Baby of the House.
Uxbridge and South Ruislip
Reason for By-Election: The resignation of Boris Johnson prior to his likely suspension from Parliament and recall as an MP.
Previous Majority: 7,210 (Conservative)
Result: Steve Tuckwell the Conservative candidate retained the seat for the Conservatives. It was expected the Labour would win the seat, however, the ULEZ policy of Sadiq Khan in London took a prime position in the campaign and likely altered the outcome.
Article Summary
By-Elections happen relatively regularly in British Politics due to resignations and deaths of MPs. These by-elections are usually extremely hard for the governing party to win and are often a referendum on the party in power in Downing Street. They are important moments as they bring national focus and provides an electoral test for parties between General Elections.
Key Terms
By-Election – An election that takes place between General Elections to fill a vacancy in the House of Commons.
Recall of MPs Act (2015) – An Act passed by the UK House of Commons that allows for an MP to be recalled from Parliament by their constituents in three specific circumstances.
Turnout – The amount of registered voters who actually do vote at an election.
Specification Links:
Edexcel: Paper 1 – 4.1 (Voting Behaviour)
AQA: Paper 1 – 3.1.2.2 (Elections and Referendums)
WJEC: Paper 1 – 2.2.3 (Voting Behaviour)
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