Grassroots Conservatives have warned Theresa May she will face a challenge to her leadership at an unprecedented summit in June.

Amid fury over delays to Brexit, local constituency chairman have reached enough support to force an emergency general meeting to discuss Ms May’s premiership and her strategy on leaving the European Union.

The prime minister was reportedly notified of the news by the head of the National Conservative Convention, Andrew Sharpe, on Monday, after more than 10 per cent of local parties signed a petition calling for her to go.

It comes as the Conservatives were braced for a mauling at the local elections amid warnings they could lose more than 800 seats in Thursday’s poll.

A meeting of 800 constituency chairmen and women and senior activists is expected to take place in June, according to The Sun.

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London East Conservatives chairwoman Dinah Glover, who organised the petition, said: ”I am extremely sad that we have had to organise this.

“Unfortunately, the prime minister is no longer the solution to the problem, but is actually the block to Brexit.”

The petition said the signatories “no longer feel that Ms May is the right person to continue as prime minister to lead us forward in the negotiations”.

“We therefore with great reluctance ask that she considers her position and resigns,” it adds.

The move is said to be unprecedented in the party’s 185-year history, and would place huge pressure on Ms May to step down as party leader.

The prime minister survived a confidence vote led by Tory backbenchers in December, which means she cannot be challenged by the parliamentary party for a year.

Conservative anger has threatened to spill over after Britain’s departure from the European Union was delayed until October, as Ms May repeatedly failed to win Commons backing for her Brexit deal.

Party bosses are expecting a “difficult night” at the polls on Thursday, as local elections are expected to crystallise anger around Brexit.

Election expert and Tory peer Robert Hayward warned that delays to Brexit and her decision to stand down as Tory leader could see the Conservatives lose more than 800 seats, with the Liberal Democrats most likely to capitalise on the collapse in Tory support.

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There are 8,374 seats up for grabs in England – the majority of which are Tory-held – at 33 metropolitan councils, 119 district councils, and 30 unitary authorities.