Race for No 10: Penny Mordaunt in fight for support after Boris Johnson’s exit makes Rishi Sunak Prime Minister frontrunner

Mr Sunak, a former chancellor, swiftly hit the threshold of 100 nominations from Conservative colleagues ahead of the deadline of 2pm on Monday.

Ms Mordaunt appears far behind but allies insist they are “confident” she will hit the target, which would see the Commons Leader face off against Mr Sunak in an online ballot of Tory party members.

But if she fails Mr Sunak will effectively receive a “coronation” from Conservative MPs and quickly succeed Liz Truss as prime minister – seven weeks after he lost out to her in the last contest.

A Government source said the new prime minister could be in place as soon as Monday if the Tory leadership contest does not progress further.

The pound, after a torrid time under Ms Truss, continued to rise and the gilt market cooled, making it cheaper for the Government to borrow money, as Mr Sunak edged towards No 10.

Mr Johnson had returned home from a Caribbean holiday as he plotted a return to No 10 less than two months after being ousted following a series of scandals, but later ruled out standing.

In a statement on Sunday evening, he said there was a “very good chance” he could have been back in No 10 by the end of the week if he had stood but admitting he could not unite his warring party.

His efforts to “reach out” to his rivals – Mr Sunak and Ms Mordaunt – to work together in the national interest had not been successful, he said, so he was dropping out.

He lagged far behind Mr Sunak in public declarations of support but claimed to have amassed at least 102 nominations.

Ms Mordaunt, who has around 26 public supporters, will be trying to convince Johnson-backers to come over to her side but Mr Sunak appeared to be the immediate beneficiary.

Foreign Secretary James Cleverly called for colleagues to back Mr Sunak as the candidate with the “most experience” and former Cabinet minister Michael Gove said the Tories must “unite behind” Mr Sunak.

But a Mordaunt campaign source said they were “very close” to the target, adding: “We are confident and Penny is working flat out to give members a choice on the ballot.”

Conservative MP Damian Green told BBC Radio 4’s Today programme: “It’s certainly way, way above the published number.

“And we’re confident of getting to 100 before the deadline of 2pm and putting the case to colleagues that Penny is the person best positioned to unify the party, she’s got support from all wings of the party already and we can then get on with the important job for the country of the various serious problems we’re facing.”

Victory for either Mr Sunak or Ms Mordaunt will mean the Tories are on to their third prime minister since they won the 2019 general election under Mr Johnson’s leadership.

Veteran Tory Sir Christopher Hope joined Labour in demanding a fresh general election, arguing it is the only solution for the next leader now the Conservative Party is “ungovernable”.