Pro-Remain MPs are facing increasing pressure after Dominic Grieve suffered a vote of no confidence by his local Conservative Party.
Tories in the long-time MP's constituency, Beaconsfield, took a stand against the former Attorney General after a "robust discussion."
Grieve among a number of pro-EU Conservatives to come under pressure in their constituencies.
Remainer MPs who could come under fire in their constituencies:
The Work and Pensions Secretary is another pro-EU MP targeted by Mr Banks in her constituency.
A prominent campaigner for Remain in the 2016 referendum, she infuriated Brexiteer Tories when she and two other Cabinet ministers publicly made clear they would oppose a no-deal Brexit, in breach of Government policy.
With a wafer-thin majority of just 346 at the last general election, her position could be vulnerable within her Hastings and Rye constituency.
The former minister last month quit his local constituency (Grantham and Stamford) association after it unanimously voted to select another candidate to fight the next general election.
Mr Boles was accused by members of "betrayal" after being in the forefront of cross-party efforts in Parliament to prevent a no-deal Brexit.
He continues to sit in the Commons as a Conservative MP and retains the party whip.
The chairman of the Commons Culture Committee successfully fought off an attempt to oust him after clashing with millionaire Brexit backer Arron Banks.
The Folkestone and Hyde MP funded a series of attack adverts in the constituency after appearing before the committee's inquiry into "fake news".
However Mr Collins was last month unanimously readopted by the local constituency association as their candidate for the next general election.
Sir Alan Duncan
The Foreign Office minister and his local constituency officers were last month forced to deny reports that he was facing a vote of no confidence.
Sir Alan, after campaigning on the Remain side for the referendum, has consistently supported the Government position on Brexit.
The Rutland and Melton MP has already been readopted as the constituency association candidate for the next general election, and local officials suggested the reports were down to mischief making.
An outspoken supporter of a second referendum, Dr Wollaston was facing the threat of a vote of no confidence when she dramatically quit the Tories in February to join the breakaway Independent Group.
The Totnes MP was one of a number of pro-EU MPs to warn that former Ukip members - dubbed "Purple Momentum" - were signing up to join Conservative constituency associations in order to oust them.