Is there a by-election if an MP changes Party?

No, by-elections are not automatically triggered if an MP changes his or her party affiliation although an MP may choose to stand down and fight the ensuing by-election under a new party label or as an independent Member.

Role of the Whips Office

Information on the role of the Government and Opposition whips in the management of parliamentary business can be found in the Commons Library briefing on the Whips’ Office.

Parliament: facts and figures

This series of publications contains data on various subjects relating to Parliament and Government. Topics include legislation, MPs, select committees, debates, divisions and Parliamentary procedure.


Due to the difficulties in compiling a comprehensive list of all floor-crossings, whip withdrawals and whip resignations, this list cannot be guaranteed to be definitive.

We are always happy to hear of any additions or amendments to the list. Please email with any comments. 

We also welcome suggestions for new lists.

Related posts

  • On 23 September 2020, the House agreed to make the proxy voting scheme permanent, following the Procedure Committee's review of the pilot scheme. It also extended the proxy arrangements for public health reasons relating to the pandemic.

  • The Fixed-term Parliaments Act 2011 creates a five year period between general elections. Early elections may only be held in specified circumstances. The Prime Minister has to make arrangements for a review of the Act between June and November 2020.