LONDON — British Prime Minister Theresa May will face a vote of confidence in her leadership of the Conservative Party Wednesday, something she vowed to contest "with everything I've got."

Graham Brady, chairman of the 1922 committee of backbench Tory MPs, confirmed he has received the 48 letters of no confidence — from 15 percent of current Conservative MPs — needed to trigger the ballot. Only Tory MPs will vote.

If she loses, a leadership contest within the party will be launched to choose the next U.K. prime minister, who would take up office without a national election.

The news came after May delayed a House of Commons vote on her Brexit deal, which had been due to take place Tuesday night. Most of those who have publicly declared they want May out are hardline Brexiteers angry that her deal, in their view, keeps the U.K. too closely wedded to the EU. The prime minister spent Tuesday touring European capitals in a bid to secure assurances from other EU27 leaders in the hope of winning over more Tory MPs.

Speaking outside No.10 Downing Street Wednesday, May warned a change of leadership now would “create uncertainty when we can least afford it” and said any new prime minister would be forced to delay or stop Brexit. The U.K. is legally bound to leave the EU on March 29, 2019, and must hold a parliamentary vote on May’s Brexit deal or else depart without a deal — an outcome predicted to cause major economic disruption.

A contest could not be completed before the January 21 deadline she has set for a parliamentary vote on her Brexit deal, May said, warning that a leadership contest “risks handing control to opposition MPs in parliament.”

Early signs for May look good. According to a count of publicly declared MPs by the BBC, 158 MPs had, as of Wednesday lunchtime, said they would back the prime minister — enough for May, who only needs a majority of one, to win. However, the ballot is secret and not all MPs will necessarily vote the way they claim publicly.

Despite the positive signs, Downing Street has already offered a major concession to restive MPs, with a spokesman for the prime minister telling Westminster reporters that the issue at stake was not “who leads the party into the next election, it is about whether it makes sense to change leader at this point in the Brexit negotiations.” That has been read by many as a signal May will not continue to lead the Tory party until 2022, the current scheduled date of the next U.K. general election.

May herself will face her MPs at an emergency meeting of the 1922 Committee in Westminster at 5.00 p.m. U.K. time, before voting opens at 6.00 p.m. The result will be announced at around 9.00 p.m.

'Govern or quit'

The prime minister put on a brave face at her weekly question time in the House of Commons, and received support from some of her backbenchers. Veteran MP Ken Clarke, from the pro-EU wing of the party, branded it “unhelpful, irrelevant and irresponsible” to push for a leadership contest so late in the Brexit process.

If she loses the vote, May could carry on as prime minister until a successor is appointed, although she could also choose to resign and let a caretaker prime minister step in.

Before being told of the confidence vote on Tuesday evening, May had toured European capitals in a bid to secure assurances over the controversial Northern Irish backstop from other EU27 leaders.

The backstop, a legal guarantee for avoiding a hard border between Northern Ireland (part of the U.K.) and the Republic of Ireland (a continuing EU member), has infuriated Brexiteers as it could mean the U.K. remaining effectively within the EU’s customs union. May’s Northern Irish backers, the Democratic Unionist Party, whose 10 MPs guarantee her parliamentary majority, are also opposed because Northern Ireland would have to operate under certain EU rules that the rest of the U.K. wouldn’t.

May pulled a vote on her Brexit deal scheduled for Tuesday amid widespread expectation it would be defeated heavily in parliament, with more pro-EU opposition parties finding common cause with Brexit-supporting Conservative rebels in opposing May’s attempt at finding a middle way.

Jacob Rees-Mogg, chairman of the Euroskeptic group of backbench Conservatives, criticized May's decision to delay the vote on her Brexit deal. "What has two years of Theresa May doing Brexit amounted to? An undeliverable deal parliament would roundly reject, if the prime minister has the gumption to allow it to go before the House of Commons," he said.

"This is not governing, it risks putting [Opposition Labour leader] Jeremy Corbyn into government by failing to deliver Brexit. We cannot continue like this. The prime minister must either govern or quit."

Supporters rally

Senior Cabinet ministers, however, publicly supported the U.K. prime minister Wednesday morning.

Chancellor Philip Hammond told Sky News he was backing May, expected her to win, and branded those within his party calling for her to be ousted “extremists” who were prepared to see the U.K. leave the EU without a deal.

Foreign Secretary Jeremy Hunt tweeted the last thing the country needed was a "damaging and long" leadership contest. "Brexit was never going to be easy but [May] is the best person to make sure we actually leave the EU on March 29."

Environment Secretary Michael Gove, who ran for the Tory party leadership in 2016, tweeted: "I am backing the prime minister 100 percent — and I urge every Conservative MP to do the same. She is battling hard for our country and no one is better placed to ensure we deliver on the British people’s decision to leave the EU."

Home Secretary Sajid Javid echoed his Cabinet colleagues: "The last thing our country needs right now is a Conservative Party leadership election. Will be seen as self-indulgent and wrong. PM has my full support and is best person to ensure we leave EU on 29 March."

Justice Secretary David Gauke told the BBC the period of uncertainty while the leadership question is resolved would be destabilizing and make it harder to make progress on a deal with the European Union. "I think it is inevitable that were she to lose the vote tonight there would need to be a delay in Article 50, I don’t think we would be leaving the European Union on the 29th of March.”

International Trade Secretary Liam Fox also voiced his support, but warned in an interview with the BBC that without new assurances on the backstop he was “not even sure” that May’s Cabinet would allow it go to a vote in the House of Commons.

Under Conservative party rules, May only has to win the confidence vote by a simple majority to remain as leader, and if she did so she could not be challenged again for a year.

However, if she is defeated as leader of the party, she will be unable to stand again. MPs would choose two candidates to replace her and it would then go to a ballot of party members.

This story has been updated with additional reporting.