Jeremy Corbyn told Michel Barnier that he was open to keeping Britain in the customs union after Brexit, a memo circulated to European nations suggests.

The Labour leader met Mr Barnier, the European Union's chief Brexit negotiator, in London on Monday, where Mr Corbyn promised to run the Brexit negotiations “very differently” if he came to power - and dangled a raft of possible concessions to the EU.

According to a memo of the meeting, drawn up after a debrief between Mr Barnier and ambassadors from the other 27 EU nations, Mr Corbyn said that he was willing to allow the UK to submit to the rulings of the European Court of Justice should he become prime minister.

The document, seen by The Daily Telegraph, also states that Mr Corbyn said he could offer a “unilateral guarantee” on the rights of EU citizens during transition.

EU diplomats believe the Labour leader was deliberately seeking to undermine Theresa May in Brexit negotiations. One source jokingly likened it to “asking for a coup d’etat”.