Former cabinet minister Sir Simon Clarke has called on Rishi Sunak to resign as prime minister.
The Conservative MP for Middlesbrough South and East Cleveland said Mr Sunak has gone "from asset to anchor" and the party faces an electoral "massacre" under his leadership.
Politics latest: Reaction to Clarke's call for PM to go
The MP said the country was "on the brink of being run by Keir Starmer's Labour for a decade or more" and if Nigel Farage "returns to the fray, as looks increasingly likely, extinction is a very real possibility for our party".
Sir Simon explained that Mr Sunak was not "solely responsible for our present predicament" but his "uninspiring leadership is the main obstacle to our recovery".
"The unvarnished truth is that Rishi Sunak is leading the Conservatives into an election where we will be massacred," he wrote in The Telegraph.
Sir Simon, who served as housing secretary under Liz Truss, was one of 11 Conservative MPs to vote against Mr Sunak'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 a number of struggles for the prime minister, including falling approval ratings and unhappiness within his party over the deportation plan for asylum seekers.
Sky's political editor Beth Rigby heard last week that "several" letters of no confidence in Mr Sunak had been submitted to the backbench 1922 Committee of the Conservative Party. A minimum of 53 would need to be sent in to trigger a leadership contest.
Speaking to the Politics Hub with Sophy Ridge on Monday, Dame Andrea Jenkyns reiterated she wanted Mr Sunak to stand down.
Sir Simon's article in The Telegraph added: "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.
Multiple Conservatives quickly rode to the prime minister'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 these people realise they have a duty to the country that is greater than their personal leadership ambitions."
Former home secretary Dame Priti Patel said: "At this critical time for our country, with challenges at home and abroad, our party must focus on the people we serve and deliver for the country.
"Engaging in facile and divisive self-indulgence only serves our opponents, it's time to unite and get on with the job."
Stalwart of the One Nation wing of the party Damian Green also 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 and get our future back."
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.
"It's time for Rishi Sunak to... call a general election."