Prime Minister Theresa May has suffered another Commons defeat after MPs voted down her approach to Brexit talks.
MPs voted by 303 to 258 – a majority of 45 – against a motion endorsing the government’s negotiating strategy.
The defeat has no legal force and Downing Street said it would not change the PM’s approach to talks with the EU.
But Labour leader Jeremy Corbyn urged Mrs May to “admit her Brexit strategy has failed” and to come forward with a plan Parliament would support.
The defeat came after the pro-Brexit European Research Group (ERG) of Conservative MPs announced it had taken a “collective decision” to abstain, because backing the motion would have amounted to an endorsement of efforts to rule out a no-deal Brexit.
Mrs May has consistently rejected calls to rule out a no-deal Brexit, but Tory Brexiteer rebels believed the wording of what was meant to be a neutral government motion opened the door to that.
The motion reiterated support for the approach to Brexit backed by MPs in votes last month, one of which ruled out a no-deal Brexit.
The voting figures showed it was not just hardline Brexiteers that failed to support the government – a number of Tory Remainers also declined to vote, as more than a fifth of the party in the Commons failed to back the government.
Five Conservative MPs – Brexiteers Peter Bone, Sir Christopher Chope, Philip Hollobone, and Anne Marie Morris, and the pro-Remain Sarah Wollaston – even voted with Labour against the motion.
Downing Street blamed Mr Corbyn for the defeat, saying he had “yet again put partisan considerations ahead of the national interest” by voting against the government’s motion.
A No 10 spokesman said the PM would continue to seek legally-binding changes to the controversial Irish backstop, as MPs had instructed her to do in a Commons vote on 29 January.
“While we didn’t secure the support of the Commons this evening, the prime minister continues to believe, and the debate itself indicated, that far from objecting to securing changes to the backstop that will allow us to leave with a deal, there was a concern from some Conservative colleagues about taking no deal off the table at this stage,” he added.
Downing Street had earlier warned that defeat could damage the prime minister’s negotiating position, as she seeks to make changes to the controversial backstop “insurance policy” in her deal to avoid customs checks between Northern Ireland and the Republic of Ireland.
ERG deputy chairman Steve Baker told BBC News the group still supported efforts to get “alternative arrangements” to replace the controversial Irish backstop plan, describing Mrs May’s defeat as a “storm in a teacup”.
But business minister Richard Harrington said ERG members should join former UKIP leader Nigel Farage’s new Brexit party, telling them: “In my view you’re not Conservatives.”
In an interview with The House magazine, he urged ministers opposed to a hard Brexit not to “give in” to the ERG by resigning.
Commenting on Mrs May’s latest defeat, Jeremy Corbyn said: “Two weeks ago, the prime minister told Parliament that her new approach could ‘secure a substantial and sustainable majority’ in Parliament.
“However, tonight’s vote has proved that there is no majority for the prime minister’s course of action.
“This can’t go on. The government can’t keep ignoring Parliament or ploughing on towards 29 March without a coherent plan.”
He added that the PM needed to admit her strategy had failed “and come back with a proposal that can truly command majority support in Parliament”.
Pro-EU Conservative MP Anna Soubry said: “The prime minister has been dealt yet another body blow. This is really serious stuff.
“What is happening is a profound lack of leadership from the very top of government.”
She said it was “chilling” that ministers were still keeping no-deal on the table when they had seen economic analysis showing that it would be “absolutely disastrous” for the country.
“What an absolute fiasco this is,” she added, blaming a “lack of leadership in both of our broken parties”.
Mrs May has promised MPs a final, decisive vote on her Brexit deal with the EU when she has secured the changes to it that she believes MPs want to see.
She believes she can secure a Commons majority for the deal if she can get legally binding changes to the backstop clause – something the EU has consistently ruled out.