Theresa May has brushed off calls for her resignation, as she vowed to fight an effort to oust her as Conservative leader and Prime Minister “with everything I’ve got”.

In a dramatic early morning statement outside the door to 10 Downing Street, Mrs May warned a change of Prime Minister would put the UK’s future at risk and could delay or halt Brexit.

She needs to secure the votes of 158 Tory MPs – half the parliamentary party plus one – in a ballot on Wednesday evening to remain as party leader.

Failure to reach this figure would trigger a leadership contest in which she could not stand. But if she wins, another challenge cannot be mounted against her position as Tory leader for a year.

Mrs May insisted she would stay on to “finish the job” she has set herself as Prime Minister of addressing priorities like the economy,  public services and housing as well as delivering on the result of the 2016 referendum.

But questions were raised over whether she was privately assuring colleagues she would step down once the Brexit process was over, after a senior Downing Street source told reporters that tonight’s vote was not about choosing a leader to take the party into the next election.

Prime Minister’s Questions
Theresa May speaks during Prime Minister’s Questions hours after being told she faces a confidence vote (House of Commons/PA)

“This vote isn’t about who leads the party into the next election, it is about whether it makes sense to change leader at this point in the Brexit negotiation,” said the source.

He insisted he was “not aware” of Mrs May floating a departure date in conversations with Cabinet ministers and backbench MPs, and declined to discuss whether she would stay on if she won the ballot by a slender margin.

“She has said on a number of occasions – in fact she said immediately after the last election in 2017 – that she would serve as long as her colleagues want her to,” he said.

“She believes it is her duty to serve as long as the party wants her to.”

Mrs May was buoyed by cheers from her own backbenches in a raucous House of Commons as she stood up for what could be her final session of Prime Minister’s Questions.

Husband Philip showed his support by watching from the public gallery, while Tory elder statesman Kenneth Clarke told MPs that a leadership contest within months of the March 29 date of Brexit would be “irresponsible and unhelpful”.

(PA Graphics)

None of the PM’s Brexit-backing critics took the opportunity to attack her, while there were strong words of support from backbenchers including Neil O’Brien (Harborough), who condemned “headbangers from all sides” for undermining her.

Mrs May resisted calls from Labour and the Scottish National Party to bring her Brexit deal immediately back before the Commons, after she pulled the “meaningful vote” expected on Tuesday. And she insisted a general election would not be “in the national interest”.

Labour leader Jeremy Corbyn denounced her actions as “totally and absolutely unacceptable”, while the SNP’s leader in Westminster Ian Blackford called on her to resign.

Mr Blackford told PMQs: “This Government is a farce, the Tory Party is in chaos and the Prime Minister is a disgrace… Prime Minister, take responsibility, do the right thing, resign.”

But Mrs May sidestepped the challenge, insisting a change of Prime Minister now would mean “delaying or stopping Brexit”.

The chairman of the Conservative backbench 1922 Committee, Sir Graham Brady, told Mrs May in a phone call late on Tuesday evening that he had received the 48 letters of no confidence from Tory MPs required to trigger a ballot on the leadership.

He announced on Wednesday morning that the vote would take place between 6pm and 8pm that day, with the result announced soon afterwards.

Immediate statements of loyalty for the Prime Minister were issued by every MP in Cabinet, including several who have been touted as possible successors.

By the time of PMQs at noon, the number of Tory MPs tweeting their intention to vote for the PM had passed 130.

Foreign Secretary Jeremy Hunt said Mrs May is “the best person to make sure we actually leave the EU on March 29”, while Home Secretary Sajid Javid said a leadership contest would be seen as “self-indulgent and wrong”.

But in a joint statement, Jacob Rees-Mogg, chairman of the European Research Group of Eurosceptic Tory backbenchers, and his deputy Steve Baker said: “Theresa May’s plan would bring down the Government if carried forward. But our party will rightly not tolerate it.

“Conservatives must now answer whether they wish to draw ever closer to an election under Mrs May’s leadership. In the national interest, she must go.”

Standing before the famous door to Number 10 on Wednesday morning, a defiant Mrs May said: “Sir Graham Brady has confirmed that he has received 48 letters from Conservative MPs so there will now be a vote of confidence in my leadership of the Conservative Party.

“I will contest that vote with everything I’ve got.”

Mrs May said securing a Brexit deal which will deliver on the result of the 2016 referendum is “now within our grasp”, and added she is “making progress” in securing reassurances from EU leaders on MPs’ concerns about the proposed backstop for the Irish border.

But she warned: “A change of leadership in the Conservative Party now would put our country’s future at risk and create uncertainty when we can least afford it.”

A new leader could not be in place by the January 21 deadline by which the PM must confirm an agreement in principle had been reached with Brussels on a Brexit deal, she said.

“A leadership election risks handing control of the Brexit negotiation to opposition MPs in Parliament,” she said.

“The new leader wouldn’t have time to renegotiate a withdrawal agreement and get the legislation through Parliament by March 29, so one of their first acts would have to be extending or rescinding Article 50 – delaying or even stopping Brexit when people want us to get on with it.”

A leadership election “would not change the fundamentals of the negotiation or the parliamentary arithmetic”, she said.

“Weeks spent tearing ourselves apart would only create more division, just when we should be standing together to serve our country. None of that would be in the national interest.

“The only people whose interests would be served are Jeremy Corbyn and John McDonnell.”

Prime ministers with shortest time in office since 1900
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Mrs May said she wants to focus on voters’ priorities like the economy, public services and housing, as well as delivering on the referendum vote.

She said she has devoted herself “unsparingly” to delivering her agenda of “building a country that works for everyone” since becoming PM, adding: “I stand ready to finish the job.”

The pound fell briefly in response to news of the challenge to Mrs May, but later rallied.

Mrs May cleared the decks to lobby Tory MPs for their backing, cancelling a planned meeting of Cabinet and a trip to Dublin for talks with Irish premier Leo Varadkar.

She is expected to speak with individual Tory MPs during the day before addressing the 1922 Committee at 5pm, immediately before the crucial vote.

There was laughter at PMQs when she repeated the words she addresses to the Speaker each week: “Today, I will have meetings – possibly many meetings – with ministerial colleagues and others.”

Labour Party chairman Ian Lavery said: “With only weeks left before Britain leaves the EU, Theresa May’s weakness and failure has completely immobilised the Government at this critical time for the country.

“The Prime Minister’s half-baked Brexit deal does not have the backing of her Cabinet, her party, Parliament or the country.

“The Conservative Party’s internal divisions are putting people’s jobs and living standards at risk.”

A senior Labour source made clear the party would continue to hold back on calling a no-confidence vote in the House of Commons, which could bring down the Government if more than half of MPs support it.

“The Government has clearly lost its majority,” said the source.

“It’s clear unable to negotiate a deal that can command a majority in the House of Commons or support in the country. We will judge the best time when to move a vote of no confidence and that will be when we judge it to have the greatest chance of success.”