Moments after the vote, Jeremy Corbyn, the leader of the opposition Labour Party, announced he would seek to oust May's ruling Conservatives by bringing a motion of no confidence.
LONDON — Theresa May suffered the biggest parliamentary defeat of any British prime minister in history Tuesday as lawmakers of all stripes crushed her plan to leave the European Union.
Moments after Theresa May lost the vote by 432 votes to 202, Jeremy Corbyn, the leader of the opposition Labour Party, announced he would seek to oust May's ruling Conservatives by bringing a motion of no confidence in the government.
May called it the "most significant vote that any of us will ever be part of in our political careers."
Corbyn said the result was "catastrophic" for the prime minister, with more than 100 of her own Conservative lawmakers voting against their leader.
The consequences are complex and uncharted. May's government will face Corbyn's no-confidence motion Wednesday but it isn't clear whether the opposition leader has the numbers to make that work.
The wider picture is that more than 30 months after Britain voted in a referendum to leave the E.U. — by a vote of 17.4 million to 16.1 million — the politicians have still not agreed how this should work.
Tuesday's vote was originally meant to happen in December but May postponed it in the face of almost certain defeat.
Now that it has finally happened, lawmakers must figure out what to do next. It's not clear whether any alternative plan has enough support, and the E.U. has said it won't budge in the concessions it has already given her.
If May and Parliament cannot agree on another course of action, Britain will crash out of the E.U. on March 29 without a deal, something most experts say would have catastrophic consequences.
Other lawmakers want a "softer" Brexit or even another referendum — dubbed "the people's vote" — which might give the public the choice between May's deal, no deal, or no Brexit at all.