British Prime Minister Theresa May is to make a last-ditch attempt to cling to power by signalling to MPs in her Conservative Party that she will not lead them into the next election.

Conservative MPs ― angry at her Brexit plan ― moved to oust May on Wednesday by triggering a vote of no confidence in her leadership of the party.

A secret ballot of MPs will be held at 6pm local time this evening and the result announced at 9pm.

In an attempt to convince her party to keep her in office for now, May will make a dramatic promise to step down before the 2020 election when she addresses her MPs this afternoon, HuffPost UK understands.

“This vote isn’t about who leads the party into the next election, it’s about whether it makes sense to change leader at this point in the Brexit negotiations,” a Downing Street spokesman said.

Speaking this morning, May warned her party that changing leader now could lead to Brexit being delayed or prevented and would “put our country’s future at risk”.

“Weeks spent tearing ourselves apart will only create more division,” she said.

But pro-Brexit Conservatives who believe her deal will keep the UK too closely tied to the European Union have dismissed the claim.

Bernard Jenkin, a senior MP who wants May replaced, said: “The UK changed prime minister in May 1940 – in the middle of a monstrously greater national crisis than this. If it has to be done, it has to be done.”

To cling on to power May will need the support of more than 50% of the 315 Conservative MPs to stay in office – 158 in total.

If the PM loses the vote, she would not be able to stand in the subsequent leadership contest.

Candidates for the leadership must be nominated by two Conservative MPs. If only one candidate comes forward, he or she becomes leader.

If a number of would-be leaders are nominated, the list is whittled down to a shortlist of two in a series of votes by MPs.

The final pair then go to a postal ballot of all party members, with the

position of leader – and prime minister – going to the victor.

Members of May’s Cabinet have all expressed public support for the prime minister and promised to back her in the vote.

Philip Hammond, the Chancellor of the Exchequer, went to war with MPs who want rid of May and said the vote would “flush out the extremists” in the party.

But even if over 158 Conservative MPs express public support before the vote May can not relax, as many could say one thing in public but then vote the opposite way in private.

The move to oust May came after she decided to postpone a parliamentary vote on her Brexit deal - which she was widely expected to lose.

Ian Lavery, the chairman of the opposition Labour Party, said May’s “weakness and failure has completely immobilised the government at this critical time for the country”.

The UK is set to leave the EU on March 29, 2019, and time is running out for a deal to be agreed.

This story has been updated throughout.

Analysis By Paul Waugh, HuffPost UK Executive Editor, Politics For many, the central flaw in David Cameron’s Brexit referendum was that it offered Britons a departure ticket without a destination. And today, as Theresa May faces an existential threat to her premiership, a similar flaw is evident in the Tory party’s leadership rules. MPs can get rid of May without having a replacement lined up. They can have their moment of ‘we’re free!’ cartharsis, but once the exhilarating whiff of liberation has faded, the realisation dawns that their leap of faith is a leap into the unknown. The instability and uncertainty of alternative options has been the threat that has kept May in power since her disastrous snap election. Yet for many of her MPs, May’s exit (can we call it Mexit?) is worth the risk. After Tory backbenchers decided to ‘take back control’ of their party leadership, they will know that any replacement PM would face the exact same Parliamentary arithmetic and the exact same deadlock over Brexit. That arithmetic can only be changed by a general election, an election that many Tory MPs in marginal seats simply can’t countenance because of the real threat of Jeremy Corbyn running yet another poll-defying election campaign that could make him Prime Minister. The Christmas chaos that this contest could provoke is obvious. It’s possible that under the newly centralised party membership system, a ballot could be held by email, but many members would want a postal vote. Add in hustings around the country, and it could be that it is the New Year before a contest could be realistically staged, May’s allies will war. That would mean May would stay on as ‘caretaker’ PM while her party picks a successor. When Owen Paterson was this morning asked when a new leader could be in place, he replied: “I would have thought mid-January…I’m not an expert.” Then again, maybe Britain has indeed had ‘enough’ of experts. Read more