Ministers had mounted an unprecedented public negotiation with Tory rebels in the House of Commons a bid to avoid defeat over the terms of a vote by MPs on the final Brexit deal.
During three and a half hours of tense debate on amendments to the EU Withdrawal Bill, government whips held whispered conferences with a handful of Tories on the Commons benches. Several MPs were ushered out for further talks by the Chief Whip, Julian Smith.
Earlier, a junior minister resigned to fight for a 'meaningful vote' for MPs, saying the government was offering a "fake choice" between "a bad deal and no deal".
Solicitor General Robert Buckland intervened four times during a speech by the former Attorney General Dominic Grieve, whose amendment would effectively give MPs a veto on the government’s negotiating agenda if a deal isn't done by the end of November. Mr Grieve's proposal will now be added to the legislation.
Opening the debate, Brexit Secretary David Davis insisted the government would abide by three principles to defend the will of the British people.
"First, we must never do anything that undermines the Government's negotiating position or encourages delays in the negotiations,” Mr Davis said.
"Secondly, we cannot change the fundamental constitutional structure which makes the Government responsible for international relations and international treaties.
“Thirdly, we must under all circumstances respect the result of the referendum. That's what this House voted on Article 50."
MPs were told that one parliamentarian had to be accompanied to a public meeting by a six armed police officers because of threats over their stance on Brexit.
Conservative former minister Anna Soubry said the abuse of MPs who speak out against the government’s Brexit policy “simply has to stop”.
Ms Soubry warned: "Never before have we been in a situation where we have a Cabinet who is so divided.
"Where some of its most senior people who hold the greatest offices of state, at every twist and turn, when our Prime Minister moves towards securing a Brexit that will serve everybody in our country, the softest, most sensible Brexit, both publicly and privately they undermine her and scupper her attempts.
"It simply has to stop and that moment is now."