U.K. Prime Minister Theresa May vowed to fight for her job Wednesday as her Conservative Party colleagues plotted a leadership challenge that could deepen the country's political crisis and add yet another layer of complexity to its ongoing Brexit drama. 

May will face a Party vote on her leadership later today after lawmakers put forth the requisite number of letters to the so-called 1922 Committee to trigger a formal leadership challenge. If she prevails, Party members can't challenge her again for at least a year. If she is voted out, the Party will name an interim Prime Minister. May said she would contest the challenge  with"everything I have got" and insisted it would put the country's Brexit ambitions at risk if she were ousted.

"A new leader wouldn't be in place by January 21 legal deadline, so a leadership election risks handing control of the Brexit negotiations to opposition (lawmakers) in Parliament," May said in a statement Wednesday.

"A new leader wouldn't have time to re-negotiate 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," she added.

The formal vote is set for around 6 pm London time, after which the votes will be counted immediately "and an announcement will be made a soon as possible in the evening," said Sir Graham Brady, who chairs the party's 1922 Committee that oversees internal matters.

News of the challenge sent the pound tumbling past a 20-month low against the U.S. dollar to 1.2484 before rebounding to 1.2530 as investors feared the result would either usher in a new leader or add to the ongoing Brexit turmoil, particularly given the fact that May had failed to extract further concessions from EU leaders on her Brexit deal yesterday and still faces the threat of it failing to pass Parliament.

Regardless of the outcome of the vote, however, the Party still faces the prospect of losing control of the House of Commons over its handling of Brexit negotiations.

May herself postponed a crucial vote on the deal she painstakingly brokered with EU officials earlier this week over fears it would be defeated, triggering the potential for a so-called "confidence vote" that could topple the government and force fresh national elections. 

May meet with German Chancellor Angela Merkel yesterday as part of a series of high-level meetings aimed at extracting more detailed assurances on the main sticking point of her Brexit framework: the so-called Irish backstop.

In essence, the backstop is a portion of the agreement that commits both the U.K. and the EU to the prevention of "hard border" between the Republic of Ireland (and EU member state) and Northern Ireland, a U.K. territory, should trade talks fall down and Britain leaves the Customs Union of the bloc.

Brexit supporters don't like the backstop agreement because Britain can't unilaterally exit from it, while Brexit opponents say the fact that it's needed in the first place suggests the Brexit deal offered to the public in the 2016 referendum simply can't be delivered.

EU leaders have said they're happy to help with "clarification" on the backstop, but have uniformly insisted that it is too late to change the text of the 585-page deal struck with May last month.