Key ministers were called in to No 10 for discussions during which pushing back next Tuesday’s vote was raised, but the prime minister’s officials insisted they would plough on despite the expected defeat.
One cabinet source told The Independent that Ms May’s lieutenants are aware of the rout they could be heading for, but added “that’s still the plan”.
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In a further bad sign for Ms May, the chair of the all-powerful backbench 1922 Committee Sir Graham Brady also called for the vote to be delayed, saying it would be the “perfectly sensible” course of action.
Even ex-prime minister Tony Blair said Ms May should pull the vote, saying he did not see the logic of going down to a heavy defeat – with some estimates suggesting the government could lose by more than 100 MPs.
The prime minister’s office sought to play down her meeting with a number of cabinet members on Thursday afternoon, saying they were “nothing to get excited about”.
One insider said afterwards: “The plan is still to deliver the vote on Tuesday.
“Everyone agreed passing the PM’s deal is the best course of action for the country. They recognise it looks difficult – but that is the plan.”
The sheer scale of the pending defeat for Ms May is beginning to look historic, with Johnny Mercer MP adding his name to the 104 Conservatives who have indicated opposition.
Another source said after the meeting in No 10: “There were conversations about Tuesday and what the f*** we do, including a delay”, but they added that the intention was to push on regardless.
Speaking to Sky News after visiting Downing Street on Thursday, 1922 chair Sir Graham said: “I don’t think there is any point in ploughing ahead and losing heavily.
“What I would like is to have the reassurance that is necessary, that will answer the concerns colleagues have and let people come in behind it.
“Now if that can be done by Tuesday, that’s fine. We can vote for the government’s motion or maybe an amendment to it that gives some reassurance, but if that reassurance isn’t available by Tuesday then there is really no sense in proceeding to a vote and losing it heavily.”
He dismissed claims that it would be technically difficult to delay the vote, saying that the House of Commons would grant a few more days to the prime minister if she asked for it.
Chief whip Julian Smith acknowledged he faces an “uphill challenge” to persuade MPs to back Ms May’s deal, but insisted that “it’s all to play for”.
Speaking to ITV News, Mr Smith insisted there was no “Plan B” ready to be unveiled if the PM’s proposals are voted down.
“There is no plan, no plan for a vote loss, this is the deal, this deal that we are putting on the table, this is the deal that we need to get through Parliament,” he said.
Asked if Ms May would survive to the end of the month as PM, Mr Smith said: “[I’m] confident Theresa May will be the prime minister after the meaningful vote and will be the prime minister at and after Christmas.”
At a lunch with political journalists ex-Labour leader Mr Blair said the prime minister should be seeking a compromise solution which can command a majority in the commons, and if that cannot be found she should allow a second referendum.
Asked if she should pull the 11 December vote, Mr Blair said: “Personally, I don’t see what the point is in going down to a huge defeat.
“But I think that’s a second-order question, but the real issue is, is she prepared to work to see what is a compromise that has parliamentary approval? My belief is that when that process goes through, she will find that there isn’t one. And if there isn’t one, that’s when my solution becomes more acceptable.”
The Independent has launched its #FinalSay campaign to demand that voters are given a voice on the final Brexit deal.