Rebel Tory MPs have joined forces with Labour to inflict a fresh blow on Theresa May’s government in a Commons Brexit vote.
It means the government will have to come up with fresh plans within three days if Mrs May’s EU withdrawal deal is rejected by MPs next week.
It could also open the door to alternatives, such as a referendum.
The government lost by 11 votes, with 297 MPs voting with them and 308 against.
The government was expecting to have 21 days to come up with a “plan B” for Brexit if, as widely expected, Mrs May’s deal is voted down.
BBC reports that Labour’s shadow Brexit Secretary Sir Keir Starmer said: “The government’s decision to delay the meaningful vote has run down the clock and increased the risk of a no-deal Brexit.
“If the prime minister’s Brexit deal is defeated next week, she must return to Parliament as soon as possible and give MPs a real say on what happens next.”
But Conservative Brexiteer Jacob Rees-Mogg said the defeat would not affect the UK’s scheduled departure from the EU on 29 March.
“It merely requires a motion to be tabled not even debated,” he said.
It comes ahead of five days of debate on the PM’s Brexit deal, which is getting under way with a speech from Brexit Secretary Stephen Barclay.
Commons Speaker John Bercow faced an angry backlash from some Conservative MPs over his decision to allow MPs to vote on the issue.
The MPs claim Mr Bercow broke Commons rules and ignored the advice of his own clerks.
Commons leader Andrea Leadsom was among MPs to challenge his ruling in a series of points of order after Prime Minister’s Questions.
Mr Bercow said he had consulted his officials but would not say whether he had taken their advice
They argued that the business motion, tabled by the government, was not amendable and said the Speaker was breaking with precedent.
Mr Bercow said he had made an “honest judgement” after consulting his clerks but rejected calls from Ms Leadsom to publish the advice he had received.
He insisted he was “not setting himself up against the government but championing the rights of the House of Commons”, adding that if people wanted to vote against the amendment they could.
The clashes in the Commons came as Theresa May launched a fresh push to convince MPs to back her Brexit deal.
The prime minister cancelled a vote on her deal last month at the last minute to avoid a humiliating defeat.
She is hoping new proposals on Northern Ireland will change enough MPs’ minds to save the deal.
But the Democratic Unionist Party have already rejected the plans, saying they are “cosmetic” and “meaningless”.
Wednesday’s defeat was the second in the space of 24 hours for the government on Brexit.
MPs, headed by former Tory ministers Oliver Letwin and Dominic Grieve, defeated the government on Tuesday on an amendment aimed at making it more difficult to leave the EU without a deal.
Labour has, meanwhile, said it will table a motion of no confidence in the government if Mrs May’s deal is voted down next week.