The joint executive secretary of the 1922 Committee has revealed he will be calling for a vote of no confidence in the Prime Minister.
Nigel Evans announced that he would be "pushing very hard" for a rule change to pave the way for a leadership contest during a meeting of the 1922 Committee this afternoon.
Under current rules, the Prime Minister cannot be challenged again as leader until December, but if changed, MPs could be given an opportunity to unseat her.
"Quite frankly, the mood is grim," Mr Evans told talkRADIO's Mike Graham.
"I will be pushing very hard for a vote on a rule change in order that MPs have the opportunity themselves to express whether or not they have confidence in the Prime Minister."
Today's meeting regarding Mrs May's leadership comes after she announced she would be willing to allow a vote on whether to hold a second referendum if MPs support her Withdrawal Agreement Bill.
Committee treasurer, Sir Geoffrey Clifton-Brown, has previously said last week that the group would not be afraid to "force her [May] out" if necessary.
"It would be infinitely preferable if she set a date rather than us force her out," he said.
"It's better that she does it than we have a vote of confidence."