cross the floor

cross the floor (third-person singular simple present crosses the floor, present participle crossing the floor, simple past and past participle crossed the floor)

1. (UK politics, of a member of a parliament) To vote against one’s own political party in parliament.
2. (UK politics, informal, of a member of a parliament) To resign from one’s political party and join another party, resulting in moving from one’s currently assigned desk or seat in the legislative chamber to a new desk or seat physically located with the other members of one’s new party.
   • 2007 June 27, Philip Webster, Francis Elliott, “How Brown led his latest recruit across the floor”, in Times of London, retrieved 9 Nov. 2008:

     Two weeks ago, Mr Davies intimated to Mr Brown that he was ready to cross the floor.

• Potentially applicable to any parliament structured according to the Westminster system (and only such parliaments).

• cross the aisle

• “cross the floor”, in Lexico, Dictionary.com; Oxford University Press, 2019–2022.