London: Former prime minister Boris Johnson returned to Britain Saturday from a Caribbean holiday aiming to launch an audacious political comeback, as Conservative rival Rishi Sunak reached the minimum threshold to contest the UK's top job.
Johnson cut short a luxury stay in the Dominican Republic to join the seemingly three-person race to replace outgoing leader Liz Truss, with allies telling British media he was "up for it".
The divisive 58-year-old Brexit architect only relinquished power in early September, two months after announcing his resignation following a Tory revolt over a slew of scandals.
His apparent bid to return to office just weeks later has already been decried by opposition politicians, and even some in his own fractured ruling party who are demanding stability and unity.
"It is simply not right to risk repeating the chaos (and) confusion of the last year," said David Frost, a right-wing formerly loyal minister appointed to the House of Lords by Johnson.
"We must move on," he urged the Tories, adding they "must get behind a capable leader who can deliver a Conservative programme" who he identified as ex-finance minister Sunak.
Frost's comments echo Dominic Raab -- Johnson's deputy prime minister -- who told Sky News an imminent parliamentary inquiry into the "Partygate" scandal that dogged his former boss could prove too distracting.
Late Friday, Sunak's allies in parliament revealed he had garnered the nominations of 100 Conservative MPs, the threshold set by the party to stand.
However, both Sunak and Johnson are yet to announce they are running, with reports that a declaration by the former was imminent.
The Tories were forced into a second, this time expedited, leadership contest since the summer after Truss dramatically announced Thursday she would stand down -- just 44 tempestuous days into her tenure.
It followed a disastrous tax-slashing mini-budget that sparked economic and political turmoil which Sunak had predicted.
In a sign of the toll from the tumult, ratings agency Moody's said Friday it had downgraded Britain's outlook, blaming in part "heightened unpredictability in policy making".
Meanwhile, the pound -- which hit a record low against the dollar in the mini-budget's immediate aftermath, but had since rallied -- slumped.
Cabinet member Penny Mordaunt, who just missed out on making the final runoff after Johnson quit, was the first to formally unveil her candidacy, on Friday.
The 49-year-old said she was running for "a fresh start, a united party and leadership in the national interest" but is already trailing her rivals by dozens of nominations.
The accelerated contest will see the Conservatives' 357 MPs hold a vote Monday on any candidates with the 100 nominations, before a possible online ballot of party members later in the week if two remain.
The Sunak and Johnson camps are reportedly seeking talks to see if there is scope for a unity deal -- although there is plenty of bad blood since the former prime minister's defenestration.
Sunak's July resignation helped trigger the government mutiny that ultimately led to Johnson's ousting.
Tory MP James Duddridge, a key Johnson ally who confirmed Friday the ex-leader was intent on standing, said Saturday that he had now secured the support of 100 colleagues.
But the claim was met with scepticism by other Conservatives, with one MP telling the BBC it was "hogwash".
Johnson has nonetheless been endorsed by several Tory heavyweights, including on Saturday ex-interior minister Priti Patel.
Meanwhile, posting a photo of Johnson on the phone to his Facebook, backbench Conservative MP Lee Anderson revealed he was backing him after "a long chat about everything past and present".
"My inbox is full of BBB (bring back Boris)," he said, referring to an acronym and hashtag used by his supporters.
But in a sign of the party's deep divisions, others such as Johnson's ex-chief of staff Steve Barclay warned against turning to him.
Former leader William Hague, Sunak's mentor, told Times Radio his return as prime minister would lead to a "death spiral" for the Tories.
Veteran backbencher Roger Gale warned that Johnson could face a wave of resignations from MPs refusing to serve under him again.
Although he remains popular with party members who could decide the contest, polling shows he is broadly disliked by the electorate, with a YouGov survey finding 52 percent opposed his comeback.
Another poll also found three in five voters now want an early general election, in line with demands from opposition parties, as Britons struggle with a worsening cost-of-living crisis.