He declared there would be no trade deal unless the text he negotiated was complied with “to the letter” – and claimed that Britain had more to lose from the failure of the talks.
“The UK has been taking a step back — two steps back, three steps back — from the original commitments,” Mr Barnier said in an interview with The Times newspaper.
“The UK negotiators need to be fully in line with what the prime minister signed up to with us. Because 27 heads of state and government and the European parliament do not have a short memory.
“We remember very clearly the text which we negotiated with Boris Johnson. And we just want to see that complied with. To the letter. And if that doesn’t happen, there will be no agreement.”
Mr Barnier has previously accused the UK of “failing to engage” on the issues of EU regulations and standards, the European Convention on Human Rights, and fisheries.
In return, the government has blamed the EU’s “ideological approach” for the lack of progress in the talks ahead of the December deadline.
However, Mr Barnier said the negotiations were about “damage limitation”.
“Brexit is lose-lose. Nobody has been able to show there’s any added value to Brexit — not so far. Not even [Nigel] Farage.
“If we don’t get an agreement then that will have even more consequences. And then, of course, those will be added to the already very serious consequences of the coronavirus crisis.
“So I think we have a joint responsibility in this very serious crisis, which affects so many families ... to do everything we can to reach an agreement and I very much hope that we will do so.”
Mr Barnier said the EU would not agree to a deal that damages the EU in the long term or “harms the integrity of the single market”.
He added: “We are less exposed because 7 per cent of our exports go to the UK, whereas for the UK it’s 47 per cent of their exports which come to the EU. So I think that it is in the interests of both sides to find an agreement.”