British MPs overwhelmingly rejected Prime Minister Theresa May’s Brexit deal for a second time on Tuesday, pitching Britain into the unknown just 17 days before it is due to split from the European Union.

The House of Commons voted by 391 to 242 to reject the divorce deal, even after May secured further guarantees from Brussels over its most controversial elements. The move risks unleashing economic chaos, as Britain is scheduled to end ties with its biggest trade partner after 46 years on March 29, no matter what.

Appealing to MPs in a voice half-breaking due to a cold, May had urged them to avoid the “economic shock” of leaving without an agreement. But she also warned eurosceptics, many of whom have campaigned to leave the EU for their whole careers, that if her deal failed, so might Brexit. May has promised to allow MPs to vote on a “no deal” option on Wednesday and if that is rejected, to decide on Thursday whether to ask the EU to delay Brexit.

“If this vote is not passed tonight, if this deal is not passed, then Brexit could be lost,” she said before the vote.

Leaders across Europe also united behind a message that this was the best and final offer Britain could expect. “There will be no third chance,” European Commission chief Jean-Claude Juncker said after his talks on Monday with May.

If MPs vote against a “no deal” exit on Wednesday, and want to postpone Brexit, the other 27 EU nations would need to agree. Their leaders will meet in Brussels for a summit on March 21-22.