London: 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.

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.

Mordaunt asks to avoid 'mudslinging'

Penny Mordaunt, a junior government minister and Royal Navy reservist who is little known to the general public, has surged to become the bookies' favourite to become Britain's next prime minister.

Voting by Conservative legislators is due to continue next week until there are two candidates, who will face a runoff vote among all Conservative party members. The winner of the party race is to be announced on Sept. 5 and will automatically become prime minister.

Mordaunt is second, while Foreign Secretary Liz Truss is in third place and seeking to become the unity candidate for those on the party's right wing who worry that Sunak lacks commitment to cutting taxes.

The contest has turned nasty.

Jacob Rees-Mogg, a Cabinet minister who supports Truss, called Sunak a socialist because of the billions he spent to keep the economy afloat during the coronavirus pandemic. Another Truss supporter, former Brexit negotiator David Frost, claimed Mordaunt did not master the detail when she worked in his department and had to be moved to another job.

Mordaunt urged the party to run a positive contest.

I don't want mudslinging, she said, adding that opponents were trying to stop me getting into the final two, when a winner will be decided by Conservative Party members.

Since Johnson resigned as party leader on July 7 after months of ethics scandals, a field of 11 candidates to replace him has been winnowed down to five.

Sunak, whose resignation as finance minister last week helped topple Johnson, is running as an experienced minster who can guide the country through the economic turbulence caused by the pandemic and the war in Ukraine. But he is facing attack from Johnson allies who consider him a turncoat.

Truss is touting her international experience, as Britain's top diplomat and a former trade secretary, and is vowing to take a tough line with the European Union in post-Brexit trade spats.

Mordaunt's chief selling points are an air of normality and a distance from the scandal-tarnished Johnson administration. She did not serve in Johnson's Cabinet.

Also in the race are former Equalities Minister Kemi Badenoch, a rising star of the party's libertarian right, and centrist backbench lawmaker Tom Tugendhat.

Both are under pressure to drop out and throw their support behind one of the three front-runners but say they will fight on and try to build support through televised candidates' debates over the weekend.

Johnson won the Conservatives a commanding parliamentary majority in 2019, but has been beset by accusations that he was too close to party donors, that he protected supporters from bullying and corruption allegations and that he misled Parliament about government office parties that broke COVID-19 lockdown rules.

He remains in office until his replacement is chosen.

Despite the clashes between the Conservative candidates, they agree on most issues. None of the contenders is seeking closer ties with the EU, and none has renounced Johnson's most contentious policies: legislation to rip up parts of the UK's Brexit deal with the bloc, and a plan to send some asylum-seekers arriving in Britain to Rwanda that is being challenged in the courts.

Tim Bale, a professor of politics at Queen Mary University of London, said the issues most important to Conservatives above all Brexit did not reflect the priorities of the country as a whole. That could be a problem for the party at the next national election, due by 2024.

There's always a potential mismatch between what a party wants because a party is much more ideological and what voters want, Bale said. (The Conservative Party) has elevated Brexit to sacred levels, and I think that sometimes blinds them to the economic realities that this country is facing.

(With inputs from AP, PTI)