Negotiators are making a “final push” to reach a post-Brexit trade deal, the European Union’s Michel Barnier said.

Mr Barnier, who is leading the EU’s team in negotiations with the UK, said it was a “crucial moment” with the current trading arrangements due to end on December 31.

He was briefing ambassadors from the 27 EU countries and MEPs about the state of the talks as time runs short for a deal to be reached.

In a sign of the intensive diplomatic activity, Boris Johnson is in “close contact” with European Commission president Ursula von der Leyen.

Downing Street sources said they were speaking “from time to time given there isn’t long left” until the end of the Brexit transition period next week.

But No 10 refused to confirm Politico reports that they spoke on Monday about proposals to address the issue of fishing rights, one of the final remaining barriers to a deal.

Speaking to reporters in Brussels, Mr Barnier said: “We are really in a crucial moment and we are giving it a final push.

“In 10 days, the UK will leave the single market.”

Earlier, the European Parliament’s former Brexit co-ordinator, Guy Verhofstadt, said the queues of lorries in Kent were a sign of things to come.

France closed its border with the UK as a result of the new strain of coronavirus that is spreading rapidly across London and the South East.

In a tweet, Mr Verhofstadt said: “We forgot what borders look like. Some thought they would remain open with or without the EU. They will now start to understand what leaving the EU really means.”

The Prime Minister continued to insist the UK will “prosper mightily” without a deal, despite warning that it could add further damage to an economy already ravaged by coronavirus.

Trade between the UK and EU will face tariffs and quotas from January 1 unless a deal is reached.

But talks in Brussels remain difficult, with “significant differences in key areas”, including fishing and rules on maintaining fair competition.

Downing Street insiders flatly rejected reports that there has been a breakthrough in the row over fishing quotas.

Reports suggested the UK had offered a cut of about a third in the amount of fish EU vessels catch in British waters over a five-year period.

That is down from an initial demand to cut it by 60% over three years, but the compromise was reportedly rejected by Brussels.

At a press conference on Monday, Mr Johnson said World Trade Organisation terms – the default if there is no deal – would be “entirely satisfactory”.

“Prosper mightily remains an extremely good description of life after January 1 either way,” he insisted.

The Office for Budget Responsibility has forecast that a no-deal outcome could result in a 2% hit to gross domestic product – a measure of the size of the economy – in 2021.

That would equate to around £45 billion being wiped off the value of the UK economy.