Theresa May has reportedly been given three months to win the support of her party or she could face a leadership challenge.
Senior figures within the Conservative Party are understood to be concerned May is leading the party towards "utter destruction" and fear a poor performance at the local elections in May could be followed by a vote of no-confidence.
"There's definitely been a further shift against her," one ex-minister was quoted as saying by the Guardian.
"If people could wave a magic wand tomorrow, she would be gone [...] if we get wiped out in London, then more will say things cannot get any better under her. The alternatives would be the utter destruction of the Tory party or a chaotic leadership election, which would at least offer some way out."
A former cabinet minister added: "It looks like these elections are going to be very bad. We could well be wiped out in London and cities like Birmingham because there is no reason to vote Tory.
"MPs think in two ways: what can I do to save my seat, and what's in it for me? I think something will then happen. People will begin to manoeuvre over the leadership. There will be a degree of panic."
May's leadership looked bulletproof when she called for snap election in April last year but a disastrous campaign saw her party lose the overall majority, leading to the PM being severely criticised from influential Tory figures.
The in-fighting within the party has dragged over Brexit negotiations, with the pro-European wing of the party and the staunch Brexiteers such as Boris Johnson and Michael Gove at loggerheads.
A former minister described May as being caught between a "rock and a hard place", given the different views within her own party.
"The Brexiters would knife her tomorrow if she steps one iota out of their imagined version of Brexit, while the Remainers hold no loyalty towards her because of the way she treated them," he was quoted as saying.
Meanwhile, Johnson has been repeatedly reprimanded by May's supporters for the way he seems to be jostling for her role. Last week, the Foreign Secretary suffered a humiliating rebuke in front of May's cabinet over a leaked report that suggested he would demand a post-Brexit dividend of £100m a week for the NHS.
However, that has not ruled him out as potential successor to May.
"The smart money may not be on him but he is a huge beast in the jungle and he cannot be ignored," sources within the party said.
"Some people think he is a liability but on the other hand he is very popular among sections of the membership, particularly women. If he is not handled properly he will go off the reservation."
To trigger a vote of no-confidence, 48 MPs have to send a letter to Sir Graham Brady, the chairman of the backbench 1922 committee, demanding a contest.