There is growing support at EU level for the vision of Brexit being presented by the leader of the UK opposition, Labour's Jeremy Corbyn.

Long derided as a Eurosceptic and unelectable by many European leaders, Mr Corbyn is now being looked to as the man who could crack the Brexit impasse.

His proposal includes keeping the UK in a customs union with the EU, a move that would help ensure no return to a hard Border.

However, British Prime Minister Theresa May has made leaving the customs union a red-line issue.

Mrs May and Mr Varadkar had discussions over a three-course meal last night of salmon, fillet of beef and fruit and cheeses.

The one-on-one between the two leaders came at the request of the British government at the end of a week where Mrs May has travelled to Belfast and Brussels.

Her team were warned in advance by Irish officials that while they were happy to host her, any Brexit discussions could only be interpreted as "talk". Ireland negotiates its position through the EU taskforce led by Michel Barnier.

Mr Varadkar said the meeting was an opportunity "to share our perspectives and for us to listen to each other".

"There is much more that unites us than divides us and time is running short," he said.

Mrs May has still to outline exactly what "alternative arrangements" she wants to the backstop that she already agreed with the EU.

The prime minister is believed to have used last night's meeting to explain her desire for legally binding changes to the Brexit deal. This has been repeatedly ruled out in recent days by Mr Varadkar and a series of key EU leaders.

Mrs May argues that without tangible changes she will not be able to get a deal through the House of Commons.

After a gruelling week of rejections, her position is now being further undermined by EU diplomats who are privately discussing the virtues of proposals being tabled by her rival, Mr Corbyn.

The Labour leader has written to the prime minister with five demands he believes would help get a majority of MPs behind a deal.

Sources believe that if any deal is to get through the UK parliament, it will need cross-party support.

"We are still very much in the party politics perspective. The only hope is that, at some point, the threat of 'no-deal' disruptions would mobilise minds in the UK," said an EU diplomat.

"For now, May is still looking at her own party rather than a nationwide consensus."

The EU says London agreeing to closer ties with the bloc after Brexit would give a clear path to avoiding the backstop ever being required.

Downing Street says it is studying Mr Corbyn's proposals but there "are obviously very considerable points of difference" with the prime minister's approach.

Staying in a customs union with the EU would limit the UK's ability to seal trade deals with other countries on its own. Mr Varadkar described the Corbyn plan as "very interesting".

"I think what Jeremy Corbyn has done is fleshed out a potential future relationship which is one that would mean a future relationship that is very close between the European Union and the United Kingdom, and I think in that regard they are very interesting," he said.

"But ultimately when dealing with these matters I deal with the democratically elected government of the United Kingdom and that is headed by prime minister May."

Speaking in Belfast, DUP deputy leader Nigel Dodds said Mr Corbyn's plan "doesn't have the support of his own party, obviously".

"The way to a majority for a deal in the United Kingdom is with the Conservative Party and the DUP," said Mr Dodds.

"I don't believe Theresa May is going to split her party in order to reach out to a Jeremy Corbyn who is going to find it difficult to bring his own party along and who can't be relied upon to deliver the Brexit which the prime minister believes people voted for."

Meanwhile, former Ukip leader and Brexit campaigner Nigel Farage has announced he will stand as a candidate for a new 'Brexit Party' to contest European Parliament elections if Britain's departure from the EU is stalled.

"The party was founded with my full support and with the intention of fighting the European elections on May 23 if Brexit has not been delivered by then," he said.

Irish Independent