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MPs' changes of party allegiance in the House of Commons since 1979

Published Monday, September 16, 2019

This list notes when a Member has changed allegiance from one political party to another or decided to sit as an independent MP. Instances of Members losing or resigning a party whip are also noted.

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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.

Commons Briefing papers SN02537

Author: Sarah Priddy

Topics: House of Commons, Members of Parliament, Political parties

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House of Commons Library

The House of Commons Library provides research, analysis and information services for MPs and their staff.