Theresa May will today face an ultimatum from Tory backbenchers to step down within days or be forced out of office swiftly after Cabinet colleagues urged her to abandon her heavily criticised Brexit Bill completely.

The Prime Minister, said to be in a "fragile state," is set to have a meeting with Sir Graham Brady, Chairman of the Conservatives’ 1922 backbench committee, at Westminster this morning, when he is expected to call on her to agree a June 10 date to announce her resignation as party leader. This would come after the three-day state visit by US President Donald Trump.

Yet such is the tense atmosphere across Whitehall some sources have suggested the inscrutable Mrs May might announce her resignation as early as today. A meeting of her senior aides has been called for 10am.

Underscoring the crisis in Government, the beleaguered PM, who on Wednesday suffered another major blow to her authority with the resignation of Andrea Leadsom, the Commons Leader – the 50th minister to go under her watch – pulled the publication of the Withdrawal Agreement Bill[WAB], due Friday, after senior colleagues expressed deep concern at the pledge to hold a vote on a second EU referendum.

David Mundell, the Scottish Secretary, expressed fears that a legally binding promise to facilitate a second EU poll would undermine the Scottish Conservatives’ argument against facilitating a second independence referendum. He was said to be “livid” that such a move could be heavily exploited by the SNP.

It is also understood he and other ministers believe Mrs May’s pledge went further than what was agreed at Cabinet earlier this week; an argument rejected by Downing St.

However, the PM met two senior colleagues, both of whom told her to abandon the reworked WAB.

Jeremy Hunt, the Foreign Secretary, is understood to have told Mrs May to pull the WAB completely, saying it was clear it would not be passed by MPs.

It was a "step too far" to ask Tory MPs to vote for it under current circumstances, he told the PM.

Sajid Javid, the Home Secretary, had a "frank discussion" with Mrs May about the WAB, making it clear he did not believe the Government should be "paving the way" for a second referendum.

The PM appointed Treasury Minister Mel Stride, a Remainer, to replace Mrs Leadsom as Commons Leader.

Mrs May’s meeting with Sir Graham is expected to seal her fate; yet some Tory MPs believe she may yet still try to cling on.

A 1922 Committee source said backbenchers expected the PM to be allowed to stay on until June 10 but warned there would be "much greater pressure" for her to go immediately if she intended to introduce the WAB unchanged.

"Hopefully what will happen is she will stand down as Tory leader on or before June 10 and she will hopefully remain as caretaker Prime Minister until such time as a new Tory leader is elected," he explained. "My feeling is that she will stay until June 10," he added.

The source said a new leader would ideally be in place by the end of the summer to get a Brexit deal through Parliament before the EU’s extended Brexit deadline of October 31.

Margot James, the Digital Minister, said: "It's all very regrettable but she's being hounded out of office because Parliament will not make a decision and the parties just have an inability to compromise. But in the end there's got to be a compromise."

In the Commons, the announcement about WAB was made by Mark Spencer, a Government Whip filling in for Mrs Leadsom.

He said: “We do intend to publish the WAB the week commencing June 3," explaining the Government had hoped to hold the Second Reading on Friday June 7 but "at the moment, we've not secured agreement to this in the usual channels" ie with Labour.

This throws up the possibility the debate and vote on WAB might not, as the PM had announced, take place in the first week back following the parliamentary Whitsun recess.

The crisis in Government came amid the backdrop of the European elections. An Ipsos Mori poll underlined the Tories are facing an historic election disaster. Nigel Farage’s Brexit Party were placed on 35 per cent, the Liberal Democrats on 20, Labour on 15, the Greens on 10 and the Conservatives on just nine.

Such a score for Mrs May’s Tories would be the party’s worst result in the European elections since they began 40 years ago.

Meanwhile, Nicola Sturgeon hit out at reports that EU citizens were being turned away from polling stations while trying to vote in the Euro-poll.

Frustrated voters took to Twitter with the hashtag #DeniedMyVote after turning up at polling booths to find they could not take part.

The First Minister said she had spoken to a Polish constituent who had been in the UK “for years but wasn’t allowed to vote...even though he’s on register”, adding: “It is outrageous.”

SNP MP Joanna Cherry, who previously raised the issue in Westminster, also said she was “shocked, but sadly not surprised, by the reports coming in from across the country”.

Labour said the Government was “solely to blame for the chaos,” saying it had been repeatedly warned of the dangers.

"From day one, the Tories have buried their heads in the sand about these elections. Even at the 11th hour when it was clear the Government’s botched Brexit deal would not pass. This has caused havoc for electoral administrators tasked with delivering a national poll with extremely short notice,” said Cat Smith, the Shadow Minister for Voter Engagement.

Downing St said it was aware of the reports about EU citizens not being able to vote but pointed out how the UK Government did not have a role in the administration of polls.

Theresa May’s spokesman said: “I can’t comment on the numbers or the accuracy of the reports at this stage. However, I do recognise there is frustration.”

He pointed out the running of polls was rightly a matter for returning officers. “It’s for them to put in place the necessary planning and contracts with suppliers to produce and deliver items like poll cards and postal votes to meet necessary timetables.”

He added: “I’m sure the Electoral Commission will take any reports seriously.”

The elections watchdog said it understood the frustration of those involved but explained the delay to Brexit had left little time to raise awareness of the legal process.

EU citizens living in the UK are allowed to vote either in their home country or in the UK for the European elections but can only vote once.