Norway Debate
The Norway Debate was a famous debate in the British House of Commons that took place on May 7 and May 8 1940. Ostensibly a debate on the conduct of the Norway campaign, the debate witnessed a massive outpouring of criticism and hostility towards the general conduct of the war and the government of Neville Chamberlain. In the vote at the end of the debate there was a sizable rebellion of government supporters who voted against their own government on what was considered a Motion of Confidence (though it was not worded as such).
Two days later Chamberlain resigned and was succeeded by Winston Churchill.