Brexit negotiator David Frost and his EU counterpart Michel Barnier ended the latest gruelling round of trade talks without a breakthrough – increasing the prospect of no deal exit at the end of the transition period on December 31. Prime Minister Boris Johnson is now on course to miss his unofficial deadline of reaching an agreement by the end of the month.

Following the talks in London on Thursday, EU chief Michel Barnier reiterated the bloc will stick to its red-lines on a so-called level playing field on trade and access to British fishing waters.

Mr Barnier insisted the continued stalemate now meant a deal looked “unlikely” and warned the “time for answers is quickly running out”.

David Frost said “considerable gaps remain in the most difficult areas” and called on the EU to recognise it was in discussions with an “independent state”.

Mr Frost insisted some progress had been made in other areas and said a deal could be reached by September but warned a no deal outcome remains possible.

He said: “We have made progress in areas like trade, trade of goods and services, transport, social security cooperation, EU programmes, participation and so on, which is good.

“But nevertheless big differences do remain, in particular with the familiar questions of the so-called level playing field and fisheries policy.

“We’re in a negotiation. Either outcome is possible. We will work energetically to get a deal but it is possible we won’t reach one.”

With less than five months to go until the formal end of the transition period, Boris Johnson now wants both sides to get to work on the texts of agreement.

A UK Government source said: “Obviously everything needs to be up for discussion, but it makes no sense to have everything going at the speed of the most difficult issues.

“Now they need to adapt their approach to make sure talks throughout the summer don’t suffer from unnecessary roadblocks.”

Brexit Party leader Nigel Farage has urged Mr Johnson to ensure the UK is “completely free of EU rules” and warned anything less will be a “betrayal” of the 2016 EU referendum and 2019 general election results.

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Mr Farage said: “He will face an EU which, through Chancellor Merkel and President Macron, feel that their project is back on track. But ultimately Frost must stay true to his word.

“And that is why the moment has now come for us to push full steam ahead to prepare for what is known as ‘no-deal’, or what the Government has chosen so far to call an ‘Australian-style deal’.

“That would mean trading on World Trade Organisation terms.

“We have to push ahead with this because it is the only way the EU will ever come to its senses.”