Conservative party associations are reporting a surge in members who have joined in the wake of Theresa May’s Chequers deal which has proved unpopular with the grassroots.

The increase in membership will raise concerns that the party is at risk from a ‘blue Momentum-style’ takeover among supporters furious with the deal which keeps Britain closely tied to the European Union after Brexit.

John Strafford, a Tory grassroots campaigner, said the rise came from former UK Independence Party members who were rejoining because they do not like the deal and want to vote in a leadership contest to replace Mrs May.

Conservative Party rules mean anyone who has been a member for more than three months can vote in a leadership contest.

The news came as Boris Johnson, the Cabinet minister who quit over the deal, reinforces his opposition to the deal on Monday, writing in The Daily Telegraph that it is time to “chuck Chequers”.