Theresa May suffered a second House of Commons defeat within 24 hours as MPs moved to force the prime minister to reveal her Brexit plan B sooner, if her EU divorce deal is rejected next week.
A group of 17 Tory rebels inflicted yet another Brexit loss for Mrs May as they joined a majority in the Commons in demanding she set out an alternative strategy within three days of any defeat on her agreement.
The government had also been defeated on Tuesday night as MPs sent a powerful signal they will not accept a "no-deal" Brexit.
The government previously had three weeks to bring forward new proposals if the prime minister's deal is rejected by MPs in their "meaningful vote", which is scheduled for next Tuesday.
The timescale was shortened thanks to a successful amendment to the Commons motion on Mrs May's Brexit deal pushed by Conservative Remainer Dominic Grieve.
It was passed by 308 votes to 297, but a decision by Commons' Speaker John Bercow to allow Mr Grieve's amendment to be put to a vote prompted a furious row.
Angry Tory Brexiteers questioned the Speaker's impartiality over Brexit in heated exchanges.
During the subsequent debate on Mrs May's deal, which resumed on Wednesday having been dramatically delayed by the prime minister before Christmas, Labour's shadow Brexit secretary Sir Keir Starmer raised the prospect of a delay to the UK's departure from the EU.
Hinting at one path of action MPs could try and force the prime minister down, Sir Keir told MPs: "There is a question of the extension of article 50, which may well be inevitable now, given the position that we are in, but of course we can only seek it, because the other 27 [EU member states] have to agree."
Sir Keir also attacked the prime minister for now pushing ahead with the vote on her Brexit deal when "nothing has changed" to the terms of her agreement with Brussels.
One of the Tory rebels, former minister Sir Oliver Letwin, used the debate to make a plea for a "cross-party agreement" on a Brexit deal directly with Sir Keir.
After pulling the vote last month due to the prospect of a significant defeat, Mrs May promised to deliver extra assurances from the EU over MPs' concerns with her deal.
The government had earlier published a series of commitments to Northern Ireland over the Brexit deal, aimed at wooing MPs opposed to the so-called backstop arrangement for the Irish border.
But, these were immediately rejected by the Tories' DUP allies, who prop up Mrs May's government at Westminster.
In a further attempt to win over sceptical MPs, Brexit Secretary Stephen Barclay told MPs the government would accept an amendment to the Brexit deal motion tabled by former Tory minister Sir Hugo Swire.
Among other things, the amendment requires the government to secure MPs' approval to either extend the Brexit transition period or trigger the backstop if no future trade deal with the EU is agreed by the end of 2020.
However, critics of Mrs May's Brexit deal told the prime minister the "meaningless" move would not convince them to back her agreement.
Tory MP Damian Collins said: "The government accepting Hugo Swire's amendment to the EU withdrawal agreement makes no difference to my concerns about the Brexit backstop arrangement.
"Anything short of a legally binding commitment from the EU that we can independently exit the backstop would be meaningless."
However, Mrs May did receive some support on Wednesday when Japanese prime minister Shinzo Abe and his Dutch counterpart Mark Rutte both pledged to try and help her win approval for her Brexit deal next week.
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Mr Abe is due to meet Mrs May for talks in Downing Street on Thursday.
The House of Lords also resumed their debate on the prime minister's Brexit deal on Wednesday, with the Archbishop of Canterbury telling peers a second EU referendum "may be required" if parliament failed to pass a compromise Brexit agreement.