British Prime Minister Theresa May will face a vote of no confidence later Wednesday, said Graham Brady, head of the Conservative Party's 1922 Committee of backbenchers.
The required threshold of 48 letters from members of parliament needed to trigger a vote of confidence in party leadership has been reached, Brady said.
The vote by Conservative Party members will be held between 18:00 GMT and 20:00 GMT, and the results will be "announced as soon as possible in the evening," he added.
In response, May addressed the media outside 10 Downing Street, saying she will contest the vote of no confidence.
A change of leadership now would create uncertainty "when we can least afford it," May said, adding that the first act of a successor if she loses would have to be extending or rescinding Article 50, the mechanism that started the two-year countdown to Britain leaving the European Union (EU) next March.
May said she has devoted herself unsparingly to delivering Brexit, concluding: "I stand ready to finish the job."
The British prime minister on Monday put the brakes on a vote on her Brexit deal in parliament in order to buy more time for further talks with EU leaders, who claimed that the deal, reached last month, will not be renegotiated.
The prime minister told a hostile House of Commons that she made the decision after acknowledging "the deal would be rejected by a signific ant margin."
In Brussels, European Council President Donald Tusk said Monday he had called a meeting of the council to discuss Brexit on Thursday and that the EU "will not renegotiate the deal including the backstop but is ready to discuss how to facilitate UK ratification."
The EU leaders are scheduled to meet as the final summit of the year is held Thursday and Friday.
May said that she is seeking the EU's assurance on the backstop arrangement in the Brexit deal to avoid a harder border between Britain's Northern Ireland and the Republic of Ireland.
Three key cabinet members, namely, British Foreign Secretary Jeremy Hunt, Home Secretary Sajid Javid and Housing, Communities and Local Government Secretary James Brokenshire, on Wednesday voiced their support for the prime minister, saying that "the last thing the country needs" is a Conservative Party election.
