If an MP swaps political party mid-term, a by-election is mandatory in 25 days.

Background

Force an MP who changes political party, (to a different political party), mid-term to resign. Making a by-election in that MP's constituency mandatory.

Additional details

Democracy and Constituents deserve the right to reaffirm their faith (or otherwise) in their MP, especially after the MP makes such a dramatic change in their personal beliefs.