London: Britain must accept a Brexit bill of at least euros 40 billion to unlock trade talks with the EU, Emmanuel Macron said Friday as Theresa May failed to rule out paying an even bigger final total.

The French president said May’s current offer of euros 20 billion is “not halfway there” and Britain would need to make a “substantial financial effort” to move the talks on.

The Prime Minister insisted the size of the “full and final settlement” would not emerge until all aspects of Brexit had been agreed. However, asked whether Britain could end up paying “many more billions” than has been offered, even up to euros 60 billion — the EU’s rumoured target — May would only say that the Brexit department will go through Britain’s financial commitments “line by line” before a crunch EU summit in December.

The Prime Minister hopes the next European Council meeting in two months’ time will be the moment EU leaders finally give the go-ahead for the start of negotiations on a trade deal. Chancellor Angela Merkel of Germany accepted for the first time that both sides must give ground for negotiations to progress, while Donald Tusk, the European Council president, said talk of deadlock was “exaggerated”.

The leaders of the other 27 EU countries agreed yesterday to begin talking among themselves about their position on a trade deal so that talks with the UK can get under way speedily if they are given the go-ahead in December.

They issued a statement expressing a wish to move on to trade talks “as soon as possible” but noted that Britain has made no “firm and concrete commitment” over the Brexit bill. Macron said “much work needs to be done”. He went on: “I would say we are far from having reached the necessary financial commitments before we can open phase two. We are not halfway there.”

Merkel said a breakthrough in December “depends to a large extent” on the UK, adding: “The topic of financial commitments is the dominating issue in that regard.” Crucially, however, she also acknowledged that “both sides have to move” and “I see the ball with Great Britain but at the same time I also see it with us”.

Asked whether she would deliver further details on the divorce bill in time to secure progress in two months’ time, May said: “I’m positive and optimistic about where we can get to in relation to the future partnership that we want with the EU, because it is not only in the interests of the British people, it is in the interests of people across the remaining 27 members of the EU as well.”

She said that Britain will also pay “relevant costs” of continued participation in EU projects that it still wanted to be a part of, in areas including science, research and criminal justice. Tusk said: “The negotiations go on and we will continue to approach them positively and constructively. I hope that we will be able to move to the second phase of our talks in December.” Jean-Claude Juncker, the European Commission president, said: “Our working assumption is not the ‘no-deal’ scenario.”

Border officials will have more than twice as many decisions regarding immigration and customs checks after Brexit, the National Audit Office (NAO) has warned. But it said that in some areas there was a reliance on “outdated technology” and manual processes.