MPs have voted to take control of Commons business in an unprecedented move to try to find a majority for any Brexit option.
The government was defeated by 329 votes to 302 on the cross-party amendment, a majority of 27.
Two ministers – Richard Harrington and Alistair Burt – resigned from the government to vote for the move.
MPs are now voting to ask for another Brexit extension if a deal has not been approved by 5 April.
Theresa May had tried to head off a defeat by offering MPs a series of votes on Brexit alternatives, organised by the government.
She said allowing MPs to take over the Commons agenda would have set an “unwelcome precedent”.
The so-called indicative votes are set to take place on Wednesday.
MPs will be able to vote on a series of options – likely to include a “softer Brexit” and another referendum – designed to test the will of Parliament to see what, if anything, commands a majority.