Reform’s ranks have been bolstered through the arrival of four former Conservatives (Image: Guy Bell/Shutterstock)
Reform UK has no fear of the law being changed to require MPs defecting from another party to fight a by-election. Nigel Farage’s party, which has a strong lead over its rivals in the polls, is confident it would thrash rivals in the majority of contests.
A petition calling for defections to trigger by-elections has won nearly 130,000 signatures and will be debated in Parliament on Monday. Half of Reform’s eight-strong group of MPs are former Conservatives who switched allegiance – Robert Jenrick, Suella Braverman, Danny Kruger and Andrew Rosindell.
Get the latest politics news – straight from our team in Westminster and more
Invalid email
You agree you are 18 or over. We use your sign-up to provide content in ways you’ve consented to and to improve our understanding of you. This may include adverts from us and third parties based on our knowledge of you. You can unsubscribe at any time. More Info.
The petition states: “When an MP decides they want to defect to another party a by-election should be automatically triggered to allow the constituents the opportunity to have their democratic right to agree or not with their elected official.”
A Reform spokesperson said: “Given that Reform has topped the last 230 opinion polls, with the latest data from More in Common putting us at 30%, any rule change would be irrelevant. Reform has all the momentum in British politics.
“If by-elections were triggered whenever an MP changed party, we would expect to sweep the board in most of them. The elections on May 7 will only prove this.”
Suella Braverman and Robert Jenrick have quit the Conservatives for Reform UK (Image: Getty)
Before the last general election, three Conservatives crossed the floor to join Labour – Natalie Elphicke, Dan Poulter and Christian Wakeford.
There is no requirement for a defector to stand down and fight a by-election but this happened twice when Tories left to join Mr Farage’s former Ukip party. Former Tory Douglas Carswell was re-elected as the Ukip MP for Clacton – the present political home of Mr Farage – with a majority of 12,404 in October 2014; fellow ex-Conservative Mark Reckless was re-elected the next month as the Ukip MP for Rochester and Strood with a majority of 2,920.
Britain’s most famous defector is Winston Churchill. He left the Tories in May 1904 to join the Liberal party. He was then elected as a “Constitutionalist” in the 1924 general election and became Chancellor in the Conservative Government.
UKIP leader Nigel Farage (left) with Douglas Carswell following his defection (Image: PA)
The Government stated in response to the petition: “It is an established constitutional principle that at UK general elections voters cast their vote for individual candidates, and not the political party they represent.
“When a Member of Parliament decides to change their party affiliation, it is for the MP to decide whether to continue to sit in the House of Commons (as a representative of their new political party or as an independent MP) or to stand down from their seat to trigger a by-election and, if they wish, seek re-election.
“There are no plans to make changes to the current arrangements.”
The constituencies with the highest number of signature supporting the petition’s call for mandatory by-elections were those which have seen Tory MPs switch to Reform – Mrs Braverman’s Fareham and Waterlooville (937), Mr Jenrick’s Newark (834), Mr Rosindell’s Romford (603) and Mr Kruger’s East Wilsthire (545).
Election Petition on Brink of Major Milestone as Reform Declare ‘We’d Sweep the Board’
A petition calling for automatic by-elections whenever an MP defects to another political party has become a significant point of debate in Westminster, with Reform UK saying it has little to fear from such a change and arguing that it could perform strongly if defectors were required to seek a fresh mandate.
The petition attracted more than 129,000 signatures before closing on March 4, 2026. That was comfortably above the 100,000-signature threshold normally considered by Parliament’s Petitions Committee for debate. MPs subsequently debated the issue in Westminster Hall on March 16.
At the centre of the argument is a straightforward constitutional question: should an MP who leaves the party under which they were elected automatically have to face voters again?
Under the current arrangements, the answer is no.
An MP who changes political allegiance can remain in Parliament without automatically triggering a by-election. The Government has said there are currently no plans to change that constitutional arrangement.
For Reform UK, however, the controversy has an additional dimension. Several of the party’s MPs previously represented other parties before joining Reform, meaning a mandatory by-election rule could potentially have direct consequences for its parliamentary group.
Rather than expressing concern, Reform has argued that it would welcome such contests.
What the petition is asking for
The e-petition called for a by-election to be automatically triggered when an MP defects to another political party.
Its central argument was that voters should have the opportunity to decide whether they still wanted their representative after that politician changed parties.
The petition stated that when an MP chooses to leave the party they represented at the general election and join another party, constituents should be given the opportunity to express their view through a by-election.
The issue is not entirely new.
There have previously been private members’ bills proposing changes to the rules surrounding MPs who change political allegiance. The House of Commons Library notes that one proposal in 2020 would have introduced a recall mechanism for MPs who voluntarily left the political party under which they were elected.
The arguments on both sides revolve around competing interpretations of the parliamentary mandate.
One view is that voters elect an individual MP and therefore the MP should be free to change political affiliation while continuing to represent the constituency.
The opposing argument is that party identity is an important part of a modern election, meaning that a change of party can fundamentally alter the political choice presented to voters.
Reform’s unusual position
The issue is particularly relevant to Reform UK because several of its MPs entered the party after previously being elected as Conservatives.
Reform’s parliamentary group has included former Conservative MPs such as Robert Jenrick, Suella Braverman, Danny Kruger and Andrew Rosindell. Their decisions to join Reform illustrate why the question of party defections has become particularly relevant to the party.
Yet Reform has said it is not opposed to the possibility of those MPs facing by-elections.
A Reform spokesperson argued that the party would expect to perform strongly if such elections were held, saying it would “sweep the board” in most of them. The comment was made in the context of Reform’s assessment of its then-current polling position and its confidence about local electoral contests.
That is a political claim rather than an independently established outcome.
By-elections are individual contests and can be affected by local candidates, turnout, campaigning, tactical voting and the circumstances surrounding the vacancy. National polling cannot establish what would happen in every individual constituency.
Nevertheless, Reform’s willingness to embrace the possibility is politically significant.
The Government’s position
The Government has taken a different approach.
Its formal response to the petition said there were no plans to alter the existing constitutional arrangements.
The Government’s position is based on the principle that voters elect individual candidates rather than formally electing political parties. When an MP changes party affiliation, they can continue sitting in the Commons under their new affiliation or as an independent.
An MP can voluntarily resign their seat and fight a by-election, but there is currently no automatic requirement to do so.
That distinction is central to the debate.
Supporters of the petition argue that the practical reality of modern British politics means party labels matter enormously to voters. Critics of mandatory by-elections argue that forcing MPs to give up their seats whenever they change affiliation could weaken the principle that MPs are elected to exercise their own judgement on behalf of constituents.
The debate therefore goes beyond Reform UK.
Why the issue has become more prominent
Party defections attract considerable attention because they can alter the political balance of Parliament without a general election.
An MP changing parties can change the composition of parliamentary groups, affect the government’s majority and alter the political representation of a constituency.
The controversy becomes particularly intense when MPs move between parties with substantially different political platforms.
In recent years, there have been several prominent examples of MPs changing allegiance. Before the 2024 general election, Conservative MPs Natalie Elphicke, Dan Poulter and Christian Wakeford all crossed to Labour.
There have also been MPs who moved in the opposite direction or subsequently joined Reform.
The absence of an automatic by-election means that voters generally have to wait until the next general election before they can directly approve or reject the new political affiliation of their MP.
For petition supporters, that can be a long period.
For opponents, however, it reflects the constitutional principle that MPs are representatives rather than delegates whose seats belong to political parties.
A debate about who voters actually elect
The question ultimately comes down to what a general-election vote represents.
When someone votes for a parliamentary candidate, they see both an individual’s name and a party label on the ballot paper.
A candidate may campaign heavily on their personal record, local issues and individual reputation. At the same time, the party they represent can be one of the most important factors influencing voters.
This creates an unavoidable tension.
If an MP is elected under one party and later joins another, supporters of the petition argue that the political choice originally made by constituents has changed.
The opposing position is that an MP remains the same elected representative, regardless of party affiliation, and should retain the freedom to make political decisions.
The House of Commons Library records both sides of this constitutional argument. It also notes that true instances of MPs crossing directly between government and the Official Opposition have historically been relatively rare.
What happened when MPs debated the petition
The parliamentary debate was held in Westminster Hall on March 16.
The Petitions Committee stressed that petition debates are general debates rather than votes on whether the petition’s request should be implemented. MPs can debate the issue and question the Government, but the conclusion of the debate does not itself create a new law.
That distinction is important.
Reaching 100,000 signatures does not mean that Parliament is required to introduce the requested policy.
Instead, the threshold gives petitioners an opportunity to have their issue formally debated by MPs.
In this case, the petition attracted 129,333 signatures by the time it closed, demonstrating substantial public interest in the question of defections.
The constituencies under particular scrutiny
Some of the strongest support for the petition reportedly came from constituencies represented by MPs who had moved from the Conservatives to Reform.
Among them were Fareham and Waterlooville, Newark, Romford and East Wiltshire.
Those constituencies illustrate why the issue is so closely connected to Reform UK’s rise.
Voters in these areas elected Conservative MPs at the 2024 general election. When those MPs subsequently changed allegiance, the political identity of the parliamentary representative changed without a new constituency-wide vote.
For supporters of the petition, this is precisely the situation in which a by-election would provide a democratic test.
For others, the original mandate belongs to the individual MP and does not automatically expire when party membership changes.
Reform’s confidence and the limits of the claim
Reform’s declaration that it could “sweep the board” if by-elections were triggered is part of the party’s wider political argument that its support has grown considerably.
However, individual by-elections cannot be predicted simply from national polling.
Local elections have repeatedly demonstrated that parties can perform differently from their national figures depending on the area, candidates and campaign circumstances.
A Reform candidate might benefit from a national trend in one constituency while facing strong local competition elsewhere.
Consequently, the statement should be understood as Reform’s political assessment rather than as a verified forecast of future by-election results.
What could happen next?
The parliamentary debate itself did not automatically change the law.
Any reform of the current system would require further parliamentary action and, depending on the mechanism proposed, potentially new legislation.
The Government’s existing response indicates that it does not currently intend to alter the constitutional arrangements governing MPs who change party.
That leaves the underlying debate unresolved.
Should MPs be regarded primarily as representatives elected in their own right, with the freedom to change political allegiance?
Or should changing party be treated as such a significant alteration to a voter’s original choice that constituents should automatically be given another vote?
The petition has ensured that those questions have received formal parliamentary attention.
For Reform UK, the controversy also presents an unusual political situation. Several of its MPs could theoretically have faced new elections under the proposed system, yet the party has publicly indicated that it would welcome the opportunity.
Whether that confidence would translate into victories across individual constituencies is something only actual elections could establish.
For now, the petition represents a significant moment in the continuing debate over party defections, parliamentary mandates and the relationship between MPs, political parties and the voters who elect them.
Its 129,000-plus signatures show that the issue has attracted substantial public interest. The parliamentary debate has put the constitutional question on the record. But changing the rules would require a further decision by Parliament.
Until then, MPs who change political parties can continue to hold their seats without automatically facing a by-election — leaving the argument over whether that should change firmly alive in British political debate.