Boris Johnson's hopes of getting Commons backing for his Brexit deal have hit a major stumbling block after MPs voted for an amendment which could force him to seek another delay.
In a special Saturday sitting, the Commons voted by 322 to 306, majority 16, in favour of the amendment by the former Cabinet minister Sir Oliver Letwin withholding approval until legislation to implement the deal is in place.
Sir Oliver, one of the MPs to have the Tory whip withdrawn after rebelling on Brexit, said it was an "insurance policy" intended to ensure the UK cannot "crash out" of the EU on October 31 without a deal.
Under the terms of the so-called Benn Act, if he does not have agreement on a deal on Saturday, the Prime Minister is required to seek a further extension to the Article 50 withdrawal process until the end of January.
Boris Johnson told the Commons: "It has been a very important debate, an exceptional moment for our country, an exceptional moment for our Parliament.
"Alas, the opportunity to have a meaningful vote has effectively been passed up because the meaningful vote has been voided of meaning.
"But I wish the House to know that I am not daunted or dismayed by this particular result and I think it probably became likely once it became obvious that the amendment from my right honourable friend, the member for West Dorset was going to remain on the order paper.
It is expected that the whips will now order Conservative MPs home without voting on the the main motion to approve the deal.
Ministers have signalled that they will press ahead with plans to table the legislation next week with a view to securing Britain's departure by the end of the month.
Several opposition leaders have welcomed the results.
Labour leader Jeremy Corbyn said: "I welcome today's vote. It's an emphatic decision by this house that has declined to back the Prime Minister's deal today, and clearly voted to stop a no-deal crash out from the European Union.
Scotland First Minister Nicola Sturgeon tweeted: "Excellent - Johnson's losing run continues and, more importantly, his contradictory promises to the ERG and Labour rebels, and his bad deal overall, can be subjected to real scrutiny."
Scottish Greens Co-Leader Patrick Harvie MSP said: “Boris Johnson has once again been defeated by democracy. His attempt to foist his rotten deal upon us, just like his attempt to unlawfully bypass parliament, has been rebuffed."
Liberal Democrats leader Jo Swinson added: "Today hundreds of thousands of people will be outside demanding a final say in a People's Vote.
"Isn't the truth that the reason the Prime Minister refuses their calls is because he knows that if given the option the people will reject this bad deal and choose to remain in the EU?"