British Conservative MP Philip Lee defected on Tuesday to the Liberal Democrats ahead of a crucial vote in Parliament on Brexit, meaning British Prime Minister Boris Johnson no longer has a working majority in the House of Commons.
Lee is the fourth MP to defect to Jo Swinson's party in the last few months and takes their total to 15.
Lee, the MP for Bracknell, crossed the floor of the House of Commons and took his seat on the opposition Liberal Democrats' benches as the prime minister began to address Parliament on last month's G7 summit in France.
Lee's defection took place ahead of a crucial vote on Tuesday night, in which rebel MPs will try to take control of the parliamentary agenda and block a no-deal Brexit.
The prime minister is facing a showdown between himself and Tory rebels over Brexit.
Johnson, who vowed to take his country out of the European Union on Oct. 31 with or without a deal, said earlier this week that he will call a snap election if he is defeated by the cross-party alliance of MPs.
In a resignation letter addressed to the prime minister, Lee said "After a great deal of thought, I have reached the conclusion that it is no longer possible to serve my constituents' and country's best interests as a Conservative Member of Parliament."
"The Brexit process has helped to transform this once great party into something more akin to a narrow faction, where an individual's 'conservatism' is measured by how recklessly one wishes to leave the European Union," Lee noted.
"Perhaps most disappointingly, it has increasingly become infected with the twin diseases of populism and English nationalism," he said.
Earlier Tuesday, Justine Greening, the former Conservative cabinet minister and Brexit rebel, announced that she will quit as an MP in the next election and criticised the Tory party for "turning into the Brexit party."
