Theresa May has vowed to fight off any leadership challenge following reports hardline Brexit Tory MPs are plotting a coup.

Last night 50 members of the European Research Group (ERG) met in Parliament and some are said to have pushed for May to be ousted.

The powerful alliance of Tory MPs want May to ditch her Chequers Brexit plan, arguing it will keep the UK too closely tied to the EU.

A Downing Street spokesman said this afternoon that May would fight any confidence motion.

“I’ve answered that question in the past. The answer hasn’t changed. The answer was ‘Yes’,” he said.

Jacob Rees-Mogg, the leader of the ERG, said Tory MPs are “entitled” to want rid of May – but insisted he is not coordinating any leadership challenge.

“We are focusing on how the policy should change. The ERG is not in any way an organisation involved with leadership issues,” he said. 

If 48 letters are handed over to Sir Graham Brady, chairman of the backbench Tory 1922 Committee, a vote of no confidence would be triggered.

However, to oust the PM as leader, plotters would need 158 Tory MPs to vote against her.

If the coup failed, party rules dictate that May would then be secure in post for at least a year.

This morning the ERG unveiled its alternative proposal for how a hard border in Ireland could be avoided.

But No 10 rejected the plan. “We have been working on the issue of the Northern Irish border for two years and we have looked at a significant number of potential solutions,” the spokesman said.

“We believe the plan put forward by Chequers is the only credible and negotiable solution.”

It comes as European Commission president Jean-Claude Juncker said Brussels will work “day and night” to reach a Brexit deal.

“The United Kingdom will never be an ordinary third country for us. The United Kingdom will always be a very close neighbour and partner, in political, economic and security terms,” he said.