The UK needs to be “educated” about the price of leaving the EU, the bloc’s chief negotiator Michel Barnier has said.
Speaking in Italy, Mr Barnier said he sees the process as an opportunity to “teach the British people and others what leaving the EU means”.
It comes as Number 10 and government ministers moved to reject claims that Theresa May is preparing to approve a divorce bill of up to £50 billion.
Mr Barnier reportedly said the UK must honour a commitment it made in 2014 to pay 14% of the EU budget until 2020.
The Sunday Times report that the Whitehall plans will see the UK pay between £7 billion and £17 billion a year to Brussels for three years after Brexit.
Number 10 sources said the claim was “not true”, while Brexit secretary David Davis told the BBC’s Andrew Marr Show the figure was “nonsense”.
Asked about the divorce bill, Foreign Secretary Boris Johnson refused to be drawn on an exact figure.
Mr Johnson said: “I have seen some pretty big figures that have been quoted about what we allegedly owe.
“I don’t think we’re, at this stage, getting in to any detail, but I think some of the things I’ve seen are very, very extravagant indeed – we certainly wouldn’t be paying anything like that amount.
“We will certainly honour our legal obligations as we understand them. What we won’t do, as Theresa May has said very clearly, we won’t continue to pay in large sums after we leave – we won’t pay for access to the EU markets.”
He added that it was “impracticable” to try to come to a final deal on the finances before getting a better sense of the final trade arrangements.
The EU is only prepared to begin trade talks once it believes “sufficient progress” has been made on issues including the divorce bill.
The financial settlement was the subject of a bitter row between Mr Davis and Mr Barnier during the latest round of negotiations on Britain’s EU withdrawal.
Responding to Mr Barnier’s comments about “educating” the EU on the price of leaving the EU, Mr Johnson said: “Of course there’s going to be difficult negotiations ahead, but in the end what I think he wants and what David Davis and Theresa May and I want, and what everybody in the UK wants, is a deal that works for both sides and a deal that delivers the maximum economic prosperity for both sides.”
The payment dispute came as Mrs May’s allies issued a warning to would-be rebels ahead of the first Commons votes on the Brexit legislation.
They claim any attempt to water down the so-called Repeal Bill will risk putting Labour leader Jeremy Corbyn in power.
The Bill – officially called the European Union (Withdrawal) Bill – repeals the 1972 European Communities Act which took Britain into the EU.
It is designed to transfer EU law into British law so the same rules apply before and after Brexit, while giving parliaments and assemblies in Westminster, Edinburgh, Belfast and Cardiff the power to drop or change them in the future.