Theresa May has angrily condemned calls for a second Brexit referendum, despite her closest allies secretly preparing for a new poll.
The prime minister hit out at predecessor Tony Blair, who on Friday told Sky News she should "switch course" and back a second referendum because of deadlock in parliament.
Yet behind the scenes, her de-facto deputy David Lidington has discussed a new poll with Labour MPs.
And her chief of staff, Gavin Barwell, was forced to deny reports on Sunday that he was planning for a second referendum.
Over the past fortnight, Mr Lidington has held a series of meetings with Labour MPs, including one on Thursday with leading campaigners for a so-called "people's vote".
This week Mrs May will attempt to salvage her Brexit deal by calling in EU ambassadors to Number 10 and sending a top government lawyer to Brussels for talks on the Irish backstop.
The government's most senior legal officer, Jonathan Jones, aims to secure a legally binding commitment that the backstop can be time-limited, which the PM hopes would deliver the necessary votes in a Commons vote on the deal.
Hitting out at Mr Blair after a bruising week which ended with a disastrous EU summit, the PM said: "I am fighting for a good deal for Britain. I will continue to fight for a good deal for Britain.
"I have never lost sight of my duty and that is to deliver on the referendum result and to do so in a way that protects British jobs, keeps us safe and protects our precious union.
"However, there are too many people who want to subvert the process for their own political interests - rather than acting in the national interest.
"For Tony Blair to go to Brussels and seek to undermine our negotiations by advocating for a second referendum is an insult to the office he once held and the people he once served.
"We cannot, as he would, abdicate responsibility for this decision. Parliament has a democratic duty to deliver what the British people voted for.
"I remain determined to see that happen. I will not let the British people down."
In his Sky News interview, Mr Blair said: "The deal that the PM's finally concluded with the EU is a deal that nobody really wants.
"So I think that the logical thing is to go back to the people and say - you're going to have to give us direction because parliament can't agree on one form of Brexit and it's clear that as a result of this negotiation our knowledge of what Brexit really means has been vastly enlarged."
But the disclosure that Mr Lidington is talking to pro-Remain Labour MPs will incense some members of the cabinet, as well as Brexiteer Tory backbenchers.
He first met a group of around 20 Labour MPs last month and last Thursday he met leading figures from the official People's Vote campaign including Chris Bryant, Ben Bradshaw, Chuka Umunna and Chris Leslie.
Mr Lidington is one of a "gang of five" in cabinet - alongside Amber Rudd, Philip Hammond, David Gauke and Greg Clark - who are said to have concluded that a new referendum may be the only way to resolve the deadlock.
On Friday, Ms Rudd, the work and pensions secretary, stepped forward as the Tories' Brexit peacemaker, calling for a ceasefire among warring Conservative MPs and for a "coalition" with moderate Labour MPs to thrash out a cross-party compromise.
But Foreign Secretary Jeremy Hunt, who believes no deal is better than a referendum, said in a Sunday Telegraph interview the UK would flourish without a Brexit deal and also confirmed he wants to stand for the Tory leadership.
Labour MP Ian Murray said that a People's Vote is now closer than ever.
"Even Theresa May's closest supporters have realised that the only way out of this Brexit shambles is to put our country's future back in the hands of the public," he said.
"There is cross-party support for a People's Vote, and we are now moving towards a parliamentary majority. It's time for Theresa May to trust the British public and for all MPs to work together to achieve a People's Vote.
Liberal Democrat Brexit spokesperson Tom Brake said a People's Vote provides the only escape route from a divisive and damaging Brexit.
"The parties must join forces to defeat the PM's friendless deal and trigger the vote and legislation necessary for a referendum. This decision must be taken back to the people, with the option to remain on the ballot paper offering us a chance to get out of this mess," he said.