Former Conservative Party chairman Grant Shapps has called on Theresa May to resign - and revealed 30 MPs and "one or two" cabinet ministers agree.
Mr Shapps compared her premiership to the ailing end of Gordon Brown and John Major's, saying: "I don't think we're heading anywhere different."
But Environment Secretary Michael Gove has hit back, saying the plot against the Prime Minister ignored the 14 million people who voted for her in the General Election.
Speculation has swirled over Mrs May's position since the party lost its overall majority in the General Election and was ramped up following her calamity-ridden conference speech on Wednesday.
Mr Shapps told Sky News that his list of discontented MPs existed "long before" the party met in Manchester and that Downing Street "pleaded" with him not to go public earlier.
But party whips forced his hand by briefing the media instead, the Welwyn Hatfield MP claimed.
He said five former cabinet ministers, one former minister and "quite a lot of the backbenchers" from both Remain and Leave sides wanted Mrs May gone, and that the list was "growing".
"We think May is a decent person doing her best - but she led us into an election with that result," he said.
Mr Shapps added that the list was "pretty much my initiative", saying: "It's completely straightforward - I'm surprised the whips think it's a good idea to publicise it. At least people now know where to come."
"We don't want to write a formal letter - we don't want to make it difficult and embarrassing. When the time is right we'll give the list to Theresa."
Under party rules, 48 MPs are needed to force a leadership contest.
Sky's political editor Faisal Islam said: "This is more than just a headache now for the PM. This is a former minister who has gone public."
Mr Shapps became the second Tory MP - after Ed Vaizey - to publicly call for Mrs May to go, while other senior figures swept to rally round her in a show of support.
Mr Gove - who ran against her in last year's leadership election - said to oust Mrs May would be a betrayal of all those who voted for her as Prime Minister in June and voted to Leave in the EU referendum.
"What part of 14 million do these people not understand?" the Environment Secretary told Sky News.
"Theresa has a strong mandate from voters.
"I'm full of admiration for the clarity with which she cuts to the heart of every issue and the strength of her vision and her approach."
And vice-chairman of the influential Conservative backbench 1922 Committee Charles Walker was scathing about the list of names.
"Number 10 must be delighted to learn that it is Grant Shapps leading this alleged coup," he said.
"Grant has many talents but the one thing he doesn't have is a following in the party. I really think this is now just going to fizzle out."
Small business minister Margot James agreed, saying Mr Shapps "lacks a base in the party".
MP Nadine Dorries also told Sky News: "If Grant Shapps has thirty names then Diane Abbott must be doing the counting."
While other backbenchers were also less than impressed: