Prime Minister Theresa May is to face an unprecedented no-confidence challenge - from Conservative grassroots campaigners.
More than 70 local association chiefs - angry at her handling of Brexit - have called for an extraordinary general meeting to discuss her leadership.
A non-binding vote will be held at that National Conservative Convention EGM.
Dinah Glover, chairwoman of the London East Area Conservatives, said there was "despair in the party".
She told the BBC: "I'm afraid the prime minister is conducting negotiations in such a way that the party does not approve."
The Conservative Party's 800 highest-ranking officers, including those chairing the local associations, will take part in the vote.
Mrs May survived a vote of confidence of her MPs in December - although 117 Conservatives voted against her.
By Nick Eardley, BBC political correspondent
Did you enjoy the Easter Brexit truce? Don't expect it to last.
Westminster will return tomorrow with many familiar tensions.
Some Conservatives are angry at the prime minister's Brexit strategy and angry that she's holding talks with Labour.
Any vote of no-confidence by local party campaigners won't be binding. But if it did pass it would be another example of the pressure in the party.
In Parliament, there are continued calls from some for a rule change to allow another confidence vote by MPs (at the moment Mrs May is safe until December, one year on from the unsuccessful challenge at the end of 2018).
One well-placed Tory said many have had enough.
Mrs May does still have backers and seems determined to get on with the job.
But any Easter calm looks set to be short-lived.
Under party rules, MPs cannot call another no-confidence vote until December 2019.
However, an EGM has to convene if more than 65 local associations demand one via a petition.
The current petition, which has passed the signature threshold, states: "We no longer feel that Mrs May is the right person to continue as prime minister to lead us forward in the [Brexit] negotiations.
"We therefore, with great reluctance, ask that she considers her position and resigns, to allow the Conservative Party to choose another leader, and the country to move forward and negotiate our exit from the EU."
It is believed to be the first time the procedure has been used.