RISHI Sunak could be crowned the next UK prime minister on Monday afternoon after winning the backing of prominent Brexiteer MP Steve Baker.

Under the rules of the leadership race, candidates need the backing of at least 100 Conservative MPs by 2pm on Monday to move to the members’ vote.

However, if only one Tory hopeful has passed the threshold, then they will automatically win the keys to No 10.

Sunak, the former chancellor, has by far the most publicly declared backers on 129, and could see enough to win the race without a vote going to the members. If it does however, Sunak could struggle.

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In the leadership election held over the summer, the MP for Richmond (Yorks) lost out to Liz Truss on a ballot of party members, despite having led every round of the voting when it was only among parliamentarians.

Boris Johnson’s team have claimed that he has also reached the required 100 MPs to enter the membership vote, but only 56 have publicly declared their support for the disgraced former prime minister.

Penny Mordaunt (below) is languishing behind on just 24 backers.

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Steve Baker, a prominent figure on the right of the Tory Party, has now publicly declared his support for Sunak, saying the return of Johnson would be a “guaranteed disaster”.

Following similar endorsements from David Frost and Kemi Badenoch, Baker’s backing is a big boost for Sunak who previously struggled to win the support of the right-wing of the party.

Baker told Sky News he was “very proud” to support Sunak – having backed Truss in the race over the summer – saying the former chancellor would deliver “competent, capable and professional government that we can rely on”.

He called Johnson a “wonderful man”, but claimed the situation was not right for him to be prime minister.

Baker said: "This isn't the time for Boris's style. I'm afraid the trouble is because of the privileges vote, Boris would be a guaranteed disaster.

"In that vote it's guaranteed there'll be a large number of Conservatives who will refuse as they see it to lay down their integrity to save him. Sixty-two MPs resigned from his government over the Pincher affair.

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"At the moment that there's a vote in the House of Commons on the privileges committee, his premiership would collapse. It's a guaranteed nailed-on failure, and we cannot allow it... I'm not willing to lay down my integrity for Boris Johnson."

Baker, the former head of the backbench Brexiteers' "European Research Group", further said Johnson would be an "amazing chairman of the party".

He added: “But what we can’t do is have him as prime minister in circumstances where he’s bound to implode, taking down the whole government within and we just can’t do that again.”

If Johnson does manage to scrape together 100 backers he could well re-enter No10 due to his support among party members.

However, many MPs are reportedly determined to prevent that happening for the sake of their party.

Sunak and Johnson held talks on Saturday, with rumours saying they could be planning a pact. However, nothing has been confirmed.

Johnson is the only potential candidate not yet to have formally announced his bid, with Sunak having done so on Sunday morning and Mordaunt on Friday.

Tory MP Damian Green, who is backing Mordaunt, insisted she will reach the 100 MP threshold before the deadline, telling Sky News: "She'll win."

Mordaunt herself told the BBC she was "very confident" about her numbers, but suggested she was not sharing her canvassing data because she was "savvy".