Theresa May is meeting Sir Graham Brady, the leader of the influential 1922 Committee of backbench MPs, as calls for her resignation within her own party grow louder.

The meeting comes as the prime minister has said she is still working with Labour on cross-party talks to break the Brexit stalemate.

However, some Tories have reportedly warned any move towards Labour’s demands for a post-Brexit customs union with the EU will spur the Conservative Party to ditch May “very quickly.”

May is facing opposition from all sides over her attempts to strike a Brexit deal amid warnings that more than 100 Tory MPs could block a compromise agreement with Labour.

Cross-party talks will resume on Tuesday in the wake of reports that May is poised to offer Labour a temporary EU customs arrangement to break the Brexit deadlock.

Tory MPs have ramped up pressure on the prime minister to set a date for her departure, with one senior MP saying the party needs to “move on.”

Sir Geoffrey Clifton-Brown, treasurer of the influential 1922 Committee of Tory backbenchers, said May should announce a “road map” for her departure after the European elections.

He told BBC Radio 4’s Today programme: “We are now having to face the prospect of European elections which none of us wanted to face. They are going to happen.

“And, I would have thought that fairly soon after that would be time for her to think about setting a schedule to find her successor. That is regardless of whether there is a deal on offer or not. We should move on as Conservatives.”

The group’s chair, Sir Graham Brady, is due to lead a delegation of senior MPs to No.10 on Tuesday to discuss the prime minister’s future.

Conservative MPs urged Ms May not to cave into Labour’s demands as they believe a softer Brexit deal would fail to command the support of the Commons.

Nigel Evans, executive secretary of the influential committee, said: “If there is a compromise that turns out to be a kind of ‘Brexit in name only’ involving anything close to a customs union, there would be more than 100 Tory MPs who would never support it.”

A string of Commons defeats on Brexit proved the prime minister “did not have room to move here”, he told the BBC.

Tory MP Lee Rowley tweeted: “My message to Theresa May (checked with thousands of residents on the doorsteps in the only place where we gained a council directly from Lab on Thurs): stop this madness.

“People didn’t vote for you to do a deal with a Marxist. Fix the backstop and stop wasting time.” The prime minister also faced a backlash from Labour when details appeared in the newspapers from the talks, with shadow chancellor John McDonnell claiming she had “blown the confidentiality” of the discussions.

He said he no longer trusts May, following reports she was prepared to give ground in three areas: customs, goods alignment and workers’ rights.

Support free-thinking journalism and subscribe to Independent Minds Labour sources said they believe two thirds of Labour MPs, including several frontbenchers, would refuse to support a deal unless there was another vote attached - a move supported by The Independent’s Final Say campaign.

MPs close to the People’s Vote campaign believe 150 to 180 out of 246 Labour MPs could block a deal, according to The Guardian.

But Labour MP Caroline Flint, who represents a Leave-voting constituency, said there was no majority for a second referendum among MPs.

She said: “I think if a deal is struck in which Labour achieves many of its goals in that deal, that it takes us up to a general election in which all parties will be able to then set out their stall, then I think that is a deal that is worth pursuing.

“And if Labour signs up to a deal that includes those goals I think a majority of Labour MPs will support that position.”

The newly-formed Brexit Party is leading the opinion polls for the upcoming European elections.

Its leader, eurosceptic figurehead Nigel Farage, said any deal between Labour and the Conservatives to keep Britain in the EU’s customs union would be the “final betrayal” of Brexit voters.

“If May signs up to this, I can’t see the point of the Conservative Party even existing,” he told Sky News.

The Independent