It comes as Britain and the bloc remain in a stalemate as they try to agree on future trade ties.
UK-EU talks ended with little progress last week amid warnings of a no-deal Brexit if key issues are not settled within weeks.
With just four months until the transition period ends, both sides have failed to resolve various sticking points, like fisheries and state aid policy.
French foreign minister Jean-Yves Le Drian has now blamed Britain for the deadlock, saying talks are not advancing because of the “intransigent and unrealistic attitude of the United Kingdom”.
He told his country’s ambassadors that the bloc of 27 nations will not buckle under pressure from London.
“On Brexit we always showed unity and proved wrong those who saw signs of an overall implosion of Europe,” he said.
“It is in staying united that we can stick to our line of a global accord.”
But Downing Street hit back, accusing the EU of making it “unnecessarily difficult to make progress”.
A spokeswoman said: “We have been clear from the outset about the principles underlying the UK approach: we are seeking a relationship that respects our sovereignty and which has a free trade agreement at its core, similar to those the EU has already agreed with like-minded countries.
“However, the EU is still insisting not only that we must accept continuity with EU state aid and fisheries policy, but also that this must be agreed before any further substantive work can be done in any other area of the negotiation, including on legal texts, making it unnecessarily difficult to make progress.
“We will continue to work hard to reach agreement and look forward to the next round taking place next week.”
It comes after Germany reportedly scrapped plans for Brexit talks at the EU ambassadors summit next week after a “completely wasted” summer of negotiations.
The German government, which currently holds the rotating presidency of the EU council, had planned to discuss Brexit during the meeting on September 2, according to the Guardian.
But an EU diplomat told the publication that Brexit has been “taken off the agenda” due to the lack of “tangible progress”.
While Angela Merkel had been pegged as a potential dealmaker when negotiations resume and enter a critical stage on September 7, the diplomat said: “Over the recent months Franco-German cooperation has gained new traction.
“Given this new reality it would be futile to wait for a white knight from Paris or Berlin to come to the rescue.”
Both sides have said September is an effective deadline for an agreement to allow time for it to be ratified before Britain leaves EU rules at the end of December.