Theresa May could face an unprecedented vote of confidence in her leadership after 70 local association chiefs signed a petition supporting one, according to reports.
They have called for an extraordinary general meeting of the National Conservative Convention to discuss the Prime Minister’s leadership of the party.
A non-binding vote is expected to be held at the meeting, which would - if it showed a lack of confidence - put pressure on the 1922 Committee of Tory MPs to find a way of forcibly removing the PM from office.
Mrs May has come under heavy criticism for her handling of the Brexit process, but survived a vote of confidence of her MPs in December.
- ITV News Political Correspondent Paul Brand explains the pressures the PM is facing and learns of two new attempts to oust Theresa May
Paul Brand said during the two week break, MPs have found a "renewed energy" to remove Mrs May from Number 10.
However he does add that party members and MPs cannot force the PM to leave her post until December under the current rules.
ITV News understands several MPs will meet on Tuesday to talk about changing the rules and the 1922 committee is said to be looking at several options including "potentially presenting the prime minister with a departure date and asking her to agree to it".
Dinah Glover, chairwoman of London East Area Conservatives, who has organised the petition, told ITV News: "She does need to go, now, and we need to reset the negotiations and set a different course.
Ms Glover added: "We do have an extension until the end of October, which actually could be used positively, but I think with Mrs May it's not going to be used positively".
Under party rules a year has to pass before another vote can be called, but an extraordinary general meeting must be held if more than 65 local associations demand one via a petition, the Telegraph reported.
Elsewhere a new poll found the former foreign secretary Boris Johnson is the favourite to replace Mrs May as Conservative leader among the party’s grassroots.
Almost a third of party members - 32.4% - backed the pro-Brexit Tory to take over the helm of the party, up by 10 points in the last month.
Ex-Brexit secretary Dominic Raab was second place with 14.7% support, according to the poll of 1,128 panel members by the Conservative Home website.
Environment Secretary Michael Gove, who also supported the Leave campaign, came third, ahead of Foreign Secretary Jeremy Hunt and Home Secretary Sajid Javid.