'Back anyone but Rishi Sunak': Boris Johnson tells allies

As the race to become Britain's next prime minister gained pace, caretaker premier Boris Johnson has reportedly told his allies to back "anyone but Rishi Sunak", according to a media report on Friday.

Johnson, who resigned as the leader of the ruling Conservative Party on July 7, has been urging defeated Tory leadership candidates not to back former chancellor Sunak, who is widely blamed for Johnson's loss of support among his own party members, The Times newspaper reported.

Johnson, who has said he will not endorse any leadership candidates or publicly intervene in the contest, is believed to have held conversations with failed contenders to succeed him and urged that Sunak should not become the prime minister.

A source close to one of the conversations said the current prime minister appeared most keen on Liz Truss, the foreign secretary, endorsed by his fiercest cabinet allies, Jacob Rees-Mogg and Nadine Dorries.

Johnson is also reportedly open to Penny Mordaunt, the junior trade minister, succeeding him instead of Sunak.

According to the report, caretaker Prime Minister Johnson and his camp are running an “anyone but Rishi” hidden campaign after feeling betrayed over the former Chancellor’s resignation which precipitated his exit from 10 Downing Street.

“The whole No.10 [Downing Street] team hates Rishi. It’s personal. It’s vitriolic. They don’t blame Saj [Sajid Javid] for bringing him down. They blame Rishi. They think he was planning this for months,” the newspaper quoted a source as saying.

Sunak, who was the winner of the first two rounds of voting by Tory members of Parliament, will appear for a series of televised debates over the weekend with his remaining opponents -- Trade Minister Penny Mordaunt, Foreign Secretary Liz Truss, former minister Kemi Badenoch and Tory backbencher Tom Tugendhat.

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An ally of Johnson rejected the claim that he wants “anyone but Rishi” to win but admitted that the outgoing prime minister harboured resentment over Sunak’s “betrayal”.

Sunak’s camp has, meanwhile, played down suggestions that his strong support does not extend beyond the Tory MPs.

"I think he really will start to connect and hopefully we can move away and offer a positive vision rather than this Conservative-on-Conservative attacks, which I really don't like," said Richard Holden, a Tory backbench MP backing Sunak.