European Union leaders are willing to allow member states to curb immigration between them to stop Britain leaving the bloc, Nick Clegg has claimed.

The former deputy Prime Minister said that they were willing to “bite the bullet” and EU countries erect border controls to stop migration between member states to stop Brexit.

Mr Clegg, the former Liberal Democrat leader who lost his seat at the general election in June, said it was “unforgivable” of Theresa May, the Prime Minister, not to try to pursue the idea.

In an interview with the Sunday Times magazine, Mr Clegg said: “I've had several conversations in the past few months, with one prime minister and one deputy head of government in the EU, who were making efforts to go much further than the package of measures David negotiated.

“If the cost of keeping the UK in the tent was a new EU-wide approach to freedom of movement, they would bite that bullet."

Mr Clegg, who is campaigning for Britain not to leave the EU in March 2019, claimed that the Government had never raised the issue in the talks about a deal to leave the EU which was set out last week.

He said: “Theresa May, unforgivably in my view, made no attempt whatsoever in the wake of the referendum to reach out privately to European power brokers and see whether there was some way she could finesse this."