Ireland’s European commissioner urges May to change course on border Brexit plan

His comments came after the Prime Minister’s DUP allies issued a warning that they would not tolerate any attempt to put barriers between Northern Ireland and the rest of the UK after Brexit.

The Prime Minister has been given until December 4 to come up with further proposals on issues including the border, the Brexit divorce bill and citizens’ rights if European leaders are to give the green light to moving on to the next phase of negotiations covering the future relationship between the UK and Brussels.

Mr Hogan, the EU’s agriculture commissioner, said it was a “very simple fact” that “if the UK or Northern Ireland remained in the EU customs union, or better still the single market, there would be no border issue”.

In a swipe at the Government’s approach to Brexit he told the Observer: “I continue to be amazed at the blind faith that some in London place in theoretical future free trade agreements.

“First, the best possible FTA with the EU will fall far short of being in the single market. This fact is simply not understood in the UK.

“Most real costs to cross-border business today are not tariffs – they are about standards, about customs procedures, about red tape.

“These are solved in the single market, but not in an FTA.”

The Prime Minister has ruled out remaining in the single market and customs union and any arrangement which appeared to give Northern Ireland a separate status would be strongly resisted by the DUP, whose 10 MPs are effectively keeping Mrs May in Downing Street after she lost her majority in the general election.

DUP leader Arlene Foster told her party conference yesterday: “We will not support any arrangements that create barriers to trade between Northern Ireland and the rest of the United Kingdom or any suggestion that Northern Ireland, unlike the rest of the UK, will have to mirror European regulations.”

Meanwhile it emerged the UK could be required to follow new rules implemented by the EU during a Brexit transition period.

The position set out by Michel Barnier in leaked documents would make the application of new EU rules a condition of a transitional deal, meaning Britain could be subject to further Brussels regulations for two years after leaving the bloc.

Mrs May hopes to secure an implementation period between the UK’s formal exit date and the commencement of any post-Brexit trade deal in order to give businesses time to adjust to the new arrangements, but accepting the imposition of new rules could trigger a revolt by Eurosceptics.

It would also go against the approach to an implementation period set out by the Prime Minister in her Florence speech, where she said the “framework for this strictly time-limited period… would be the existing structure of EU rules and regulations”.

The Independent obtained a presentation drawn up by Mr Barnier for representatives of the 27 remaining EU members in which he said a transitional deal would involve the “automatic application in the UK of new EU rules post-30 March 2019”.

Foreign Secretary Boris Johnson has already indicated that accepting further regulations from Brussels would cross a red line.

The Prime Minister was also under pressure not to water down a red line on the European Court of Justice’s jurisdiction ending when the UK leaves the EU.

The Sunday Telegraph reported that Brexiteer ministers and backbenchers have expressed alarm at a plan being pushed in the Cabinet’s Brexit sub-committee for the UK to agree to a system of “voluntary referral” of cases to the Luxembourg court.

Shadow international trade secretary Barry Gardiner said that Labour had not ruled out staying in the single market or a customs union with the European Union after Brexit.

He told BBC One’s Andrew Marr Show: “It’s not our call and it would be foolish of an opposition to actually put out there and say this is the solution, when we’re not in the negotiating table itself.

“If we’re at the negotiating table, we can have those discussions. I’d be very happy if Theresa May wanted to move over and call that election and let us do that.

“But until we’re round that table, it’s not sensible to say what you can get out of the negotiations, because you’re not sitting there like you and I are, looking at the whites of each other’s eyes and getting a deal.”

Scottish Tory leader Ruth Davidson claimed that a last-minute deal would be agreed and acknowledged it would be a setback if there was not progress at the December summit.

“The people that walk up to the microphones and speak to their home audience don’t always reflect the negotiation and the progress that is going on in the room,” she told Andrew Marr.

“When it comes to European negotiations it’s always a five-past-midnight job.”

Ms Davidson said that unless progress on to the next phase is made in December “we are rapidly going to run out of time” for a transitional deal to be put in place.

“I don’t think it means that the world has ended but I do think it’s a setback,” she said.