The European Union's chief negotiator in Brexit talks has said he is "worried and disappointed" about the lack of compromises being made by the British government.

Michel Barnier warns that "make no mistake" there will be a "huge difference between a deal and a no-deal" when the United Kingdom completes its exit from the bloc at the end of this year.

The UK formally left the EU at the end of January, and is in a transition period which lasts until Dec 31, during which time the two sides are supposed to agree terms for future trading relations.

But with time running out and Prime Minister Boris Johnson having consistently rejected the suggestion that there might be any kind of extension to the transition, the prospect of a no-deal Brexit, which would see the UK have no alternative trade agreements in place for its dealings with the 27 EU member states, grows larger.

Talks this year have been disrupted by the novel coronavirus, and the latest round began earlier this week, between Barnier and his British counterpart, David Frost.

In a speech in Dublin, Barnier said the EU has given ground to the British side but the gesture had not been reciprocated.

"We are ready to make fair and constructive compromise but not at the detriment of the EU," he said."I've shown clearly openness to find compromise ... If (the UK) don't move on the issues which are the key issues of the EU ... the UK will take itself the risk of a no-deal."

'Strict deadline'

He also reiterated that the end of October was a "strict deadline" to any agreement on future relations to be reached.

A spokesman for Johnson said "major difficulties remain" and it was "clear (a deal) will not be easy to achieve", despite Johnson having won a general election last December on the slogan of Get Brexit Done, and spoken of having an "oven-ready" deal.

The New European newspaper reports that at a recent event hosted by French employment federation Medef, Barnier explained some of the fundamental divisions between the two sides.

"The single market," he said, "is an ecosystem that we have been building for 60 years－with the British.

"It is made of common standards, common regulation, common supervision－maybe a bit excessive sometimes－common jurisdiction－the European Court of Justice.

"That is the single market. I can do many favors in these negotiations but the British must understand that we won't do any deal that would weaken the single market.

"If the British want to send us their products with no tariffs and no quotas, they must respect the rules of the game, a level playing field."

He said he was on a "mission" to "protect the interests, businesses and citizens in the single market", and concluded "Brexit is a lose-lose situation and we are in a situation of damage limitation anyhow.

"In four years, nobody has ever been able to show me the advantages of Brexit. Nobody."