THERESA May is locked in a Mexican stand-off with hardline Brexiteer chiefs after she dramatically opened the door to quitting as PM.

The Sun can reveal that Mrs May has indicated for the first time that she would consider resigning in exchange for MPs passing her Brexit deal.

The major admission came in a private conversation with senior Tory Eurosceptics at her Chequers country retreat on Sunday evening.

But Mrs May also made it clear she would first need to know if the numbers were there for any resignation pact before she agrees to ponder it any further.

One of the Brexiteers that Mrs May had the key conversation with was ex-Tory leader Iain Duncan-Smith, a long-standing close ally of hers.

He is now leading delicate behind the scenes efforts to try to talk round diehard Brexiteers to agree to the deal that could end the four month Brexit logjam that has paralysed Westminster.

It also emerged that IDS, Boris Johnson and Jacob Rees-Mogg have all privately told friends they are ready to vote for the divorce deal if the PM sets a date to quit.

TRUST BETWEEN NO10 AND ERG AT AN ALL-TIME LOW
But with trust between the arch-Brexiteer 60-strong European Research Group and No10 at an all-time low, many of their Tory MP diehards are insisting on a public declaration from Mrs May first.

The DUP’s 10 MPs, whose votes are also crucial to passing the deal, make up the third pillar of the tense stand-off.

The Ulster unionists have also signalled to allies that they too are ready to back the PM’s EU agreement, but only at the last minute once the ERG have said they will.

A senior Tory Brexiteer told The Sun: “It’s a tree way Mexican stand-off.

“There is a way through all this if everyone jumps at the same time - the PM, the ERG or the DUP.

“But nobody wants to be the first to move.”

The senior figure added: “The problem is we know how Mexican stand offs usually end”.

The dramatic development emerged as Westminster came close to boiling point as MPs fought over Brexit’s fate.

In a disaster for Mrs May, Parliament succeeded in a dramatic bid to seize control of Brexit.

Her Government was defeated by 329 v 302 votes in in the Commons by a backbench plot to take control of the agenda on Wednesday to hold a series of indicative votes.

Whatever Brexit alternative MPs pick could then be turned into law next week, from a softer deal to a second referendum.

Three Remain ministers resigned to back the revolt, lead by Tory grandee Sir Oliver Letwin.

They were Health minister Steve Brine, Industry minister Richard Harrington and Foreign Office Minister Alistair Burt.

More than 100 Tories are ready to back a Norway-style soft Brexit if MPs win the right to choose a different type of Brexit, it was claimed.
Mr Duncan-Smith has told fellow Brexiteers that he thinks it’s vital Mrs May “should be allowed to go with dignity”.

But the ex-Tory chief’s bid to broker a grand deal sparked a major split in the ERG, as others – lead by the group’s deputy Steve Baker- insisted they would still hold out.

Another senior ERG member told The Sun: “We will not agree to any deal with her going, because we cannot trust her to go through with it.

“She will recant the moment she gets her EU agreement through the house.”

The senior trio of Boris, IDS and Mr Rees-Mogg believe a new Prime Minister would salvage their hopes of less ties to Brussels by carrying out a negotiation for a different trade deal than Mrs May’s vision.

Their switch would bring potentially dozens of other Tory ERG members with them, putting Mrs May’s deal within touching distance of passing.

Despite swirling plots, No10 publicly refused to discuss any plans for Mrs May’s resignation yesterday.

The PM’s official spokesman said: “I don’t think it’s a matter for me to discuss with her”.

Leading Brexiteer Jacob Rees-Mogg told a meeting of the ERG group that he would vote for the deal if the DUP support it.

He said the DUP's support "makes things very different" but said assurances they want over threats to the union have not been granted "at the moment".

But DUP MP Sammy Wilson told the same meeting that the DUP remain opposed.

Around half of the 60-strong ERG was said to be in favour of backing the deal if the DUP back it.

ERG member Andrea Jenkyns described reports she was ready to vote for the deal as "fake news".

She declared: "I am not turning, I have no intention of voting for the PM's deal. I do not want to see our great country tied to the EU indefinitely."

Downing Street would not deny The Sun’s revelations.

A spokesman for the PM said: “We never comment on private meetings”.