THE European Union is "open" to a maximum two-year Brexit delay, Michel Barnier, its chief negotiator, has confirmed.

The intervention came just before Michael Gove, the Cabinet Office Minister, and David Frost, Boris Johnson’s chief negotiator, were due to appear before a Commons committee about the progress, or lack of it, in Britain’s trade talks with Brussels.

In a letter to the Westminster leaders of the SNP, the Liberal Democrats, Plaid Cymru, the SDLP, the Green Party and the Alliance Party, Mr Barnier said the option of an extension to the Brexit transition period was available if the UK wanted it.

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The leaders of these parties had previously written to the EU chief negotiator on May 15 calling for a two-year extension to be agreed between the UK and the EU amid the growing negotiations deadlock.

Ian Blackford for the SNP welcomed the letter and called on the Prime Minister to accept the offer to help protect the economy during the coronavirus pandemic.

The Brexit transition began when the UK legally left the EU on January 31 and is due to conclude at the end of the year.

The Government has repeatedly said the transition period will not be extended beyond December 31.

This was echoed by Mr David Frost, who told the Commons Committee on the Future Relationship with the European Union the Government would not be extending the transition period beyond the end of the year.

"That is the firm policy of the Government that we will not extend transition period and if asked we would not agree to it," declared Mr Frost, who stressed that by keeping to the December 31 deadline the UK would more "significant" payments to the EU.

In his letter, Mr Barnier explained: "Such an extension of up to one or two years can be agreed jointly by the two parties. The European Union has always said that we remain open on this matter.

"Any extension decision has to be taken by the Joint Committee before July 1 and must be accompanied by an agreement on a financial contribution by the United Kingdom."

Responding to the letter, Mr Blackford said: "Boris Johnson must finally put his responsibilities to jobs, living standards and the economy first and urgently agree the two-year extension on offer to the transition period.

"It would be madness to pile a Brexit crisis on top of the coronavirus crisis we already face with unemployment soaring, businesses shedding jobs, and many struggling to survive.

"Time is running out. There is just a month left to agree an extension to prevent the UK crashing out with a devastating bad deal or a catastrophic no-deal.”

The Highland MP added: "If the Prime Minister fails to agree an extension, he will be responsible for every job lost, every income slashed, and every business that goes under as a result of his bad Brexit deal.

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"The SNP will continue to press for a long extension to protect Scotland's economy - but the only way to guarantee Scotland's interests and protect our place at the heart of Europe is to become an independent country."

Layla Moran, the Lib Dem leadership candidate, urged Mr Johnson to "put his pride aside" and agree to an extension of the transition period.

She said: "The transition period was designed to give us time to secure a trade deal and make preparations for it to come into effect.

"That time has already, and understandably, been decimated by the Coronavirus response. This makes a dangerous No-Deal Brexit more likely at the end of the year, unless we extend the transition period.

"I am urging the Prime Minister to put his pride aside, tackle the crisis in front of him and take the extension he's being offered," added the Oxford MP.

At the committee, Mr Frost confirmed Mr Johnson would take part in top-level talks next month on the UK's future trade relationship with the EU.

"The expectation on both sides is that these are done at leader level and, therefore, yes, the Prime Minister would attend."

Mr Frost was speaking after the third round of talks with the EU on future trade relationships.

Asked about the role of Dominic Cummings, the PM’s chief adviser, in the Brexit negotiations, Mr Frost said he had never been given any instruction by him.

Conservative MP Peter Bone asked: "What's your relationship with Dominic Cummings, do you have to report to him? Because he seemed to say this weekend that he was the gatekeeper to the Prime Minister and he decided who spoke to the Prime Minister about what. I mean, are you more senior to him or do you have to go through him?"

Mr Frost stressed he reported to Mr Johnson on the conduct of the negotiations and to the committee.

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"What I can say is I've never had an instruction on these negotiations from Mr Cummings and I don't think he would expect to give me one. He regards me as responsible for the negotiations because the Prime Minister gave me that task."

Britain’s chief negotiator dismissed a suggestion that the UK Government's Brexit policy could "collapse" without Mr Cummings' involvement.

"The Brexit policy is set by the Prime Minister and by the committee, so I'm quite confident that, whatever the arrangement for special advisers, can continue," he insisted.

Mr Frost said the UK believed the EU's approach "in key areas is not a mandate that is likely to produce an agreement that can be agreed with us".

He told MPs: "If you're asking: do we think the EU needs to evolve its position to reach an agreement, yes, we do."

Mr Gove, asked to estimate the number of additional customs declarations UK firms would have to make from January 1 2021, said work was continuing with the business sector to determine the exact number and the staff required to process them.

Labour's Hilary Benn, the committee Chairman, said he had asked Mr Gove how many of the additional 50,000 customs agents had been recruited with the minister replying by letter that it was “not possible to put a number on it".

Pressed on this, Mr Gove said the Government "stands behind the need to ensure we increase capacity" before adding: "We have seen more than 20,000 training courses being undertaken."

On the fraught issue of fishing rights, Mr Frost said Mr Barnier had to work within the mandate given to him by member states with their "unusual" desire for the Common Fisheries Policy to continue.

“To be fair, Mr Barnier has given a few public signals that he thinks this may not be a completely realistic position and we'll have to see if they can move forward on that. Clearly it's not a runner for us."

Later, the chief negotiator said it was the job of a "good negotiator", which he said Mr Barnier was, to "assess reality and the genuine positions of the other side and a genuine ability to move".

Mr Frost added: "If you don't assess reality in a cold way then you don't get agreements, and I would expect that he'd be doing that, in fact I'm sure he is."