Former cabinet minister Sir Simon Clarke has called on Rishi Sunak to resign as prime minister.
The Tory MP for Middlesbrough South and East Cleveland, who served as housing secretary under Liz Truss, said in The Telegraph: "Rishi Sunak has sadly gone from asset to anchor."
Politics latest: Reaction to Clarke's call for PM to go
He added: "It is time to strip away illusion, and stop tolerating any indulgence of it.
"Our country, with all the challenges we face, is on the brink of being run by Keir Starmer's Labour for a decade or more.
"If Nigel Farage returns to the fray, as looks increasingly likely, extinction is a very real possibility for our party.
"And it is now beyond doubt that whilst the prime minister is far from solely responsible for our present predicament, his uninspiring leadership is the main obstacle to our recovery."
Sir Simon, a staunch ally of Mr Sunak's short-lived predecessor, was one of 11 Conservative MPs to vote against the prime minister's Rwanda bill last week after what was mooted to be a sizeable rebellion fizzled out following attempts to toughen up the scheme failed.
His intervention comes amid myriad struggles for the prime minister, including falling approval ratings and unhappiness from across the political divide with the Rwanda deportation plan.
He said: "I know many MPs are afraid another change of leader would look ridiculous. But what could be more ridiculous than meekly sleepwalking towards an avoidable annihilation because we were not willing to listen to what the public are telling us so clearly?
"A change of leadership would not have to be a protracted affair. As was planned in October 2022, the contest need only take a week.
"Two days of MPs voting, a few more days before an online members' vote. Which is worse: a week of chaotic headlines in Westminster, or a decade of decline under Keir?"
Sir Simon has also been critical of government policy on housing and wind power.
Sir Simon's calls were backed by Nadine Dorries, a Boris Johnson loyalist who resigned from the House of Commons last year and who regularly speaks out against Mr Sunak.
Two senior Conservatives almost instantly rode to the prime minster's defence.
Former defence and trade secretary Sir Liam Fox said: "This is not the time for self indulgence and tribalism in the party.
"Those who have an agenda to destabilise the government in an election year should understand the consequences.
"Having been on the front bench for all 13 years in opposition, it is a miserable place. Be warned.
Former Brexit secretary Sir David Davis said: "This is getting silly.
"The party and the country are sick and tired of MPs putting their own leadership ambitions ahead of the UK's best interests.
"It is really about time that these people realise they have a duty to the country that is greater than their personal leadership ambitions."
James Daly, the Tory MP for Bury North said: "This is absolute nonsense. The Conservative Party must unite behind the prime minister to stop the boats, continue levelling up our country and ensure equal opportunity for all.
"Everything else is self indulgence of the highest order."
Former home secretary Priti Patel and stalwart of the One Nation wing of the party Damian Green condemned Sir Simon.
Opposition parties were similarly unimpressed.
Labour's shadow paymaster general, Jonathan Ashworth, said: "This is a failing, divided government incapable of gripping problems facing the country from the cost of living crisis to state of the NHS.
"More proof that after 14 years it's time for change. Only Labour has a plan to turn the page & get our future back."
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Liberal Democrat deputy leader Daisy Cooper said: "It is utterly ludicrous that the Conservative Party is even discussing installing a fourth prime minister without even giving voters a say.
"The Conservatives are once again fighting like rats in a sack while families face soaring bills and an NHS crisis.
"People are sick and tired of this never ending Conservative Party soap opera. It's time for Rishi Sunak to give voters the chance to put an end to this farce and call a general election."