Video report by ITV News Political Correspondent Libby Wiener
Brexit Secretary David Davis has rejected claims Britain faces a soaring bill from Brussels for the EU exit, telling ITV's Good Morning Britain: "We will not be paying €100 billion."
The rising demands for the cost of the divorce from €60bn (£50bn) to €100bn (£84bn), as reported by ITV News Political Editor Robert Peston, is understood to be on Germany and France's instruction.
European Commission's lead Brexit negotiator later said the UK needs to honour its share of financial obligations, though insisted "there is no Brexit bill" - simply a "settling of accounts".
"This is not a punishment, nor is it an exit tax of some kind," Michel Barnier said at a Brussels press conference.
Mr Davis said Britain has not yet been given a "divorce deal" figure but said the European Commission lacked the power to set it.
He told Good Morning Britain that Brussels would only get what it is legally owed as he dismissed reports of the hiked up costs, which are purported to include contributions to post-Brexit farming.
"We have not seen a number," Mr Davis said. "We have said we will meet our international obligations, but there will be our international obligations including assets and liabilities and there will be the ones that are correct in law, not just the ones the Commission want."
Asked how the figure would be decided, Mr Davis said: "We will (negotiate) in the meeting, we will do it properly, we will take our responsibility seriously.
"What we've got to do is to discuss in detail what the rights and obligations are."
His rival negotiator Mr Barnier later said the UK would have to "close the account" in a "single financial settlement" which "will cover all the financial relations between the United Kingdom and the European Union. All the commitments entered into as a member of the union".
Speaking in Brussels, Mr Barnier said: "The union and the United Kingdom have mutual commitments. They have committed to financing projects and programmes together.
"We decided these programmes together. We benefit from them together, and we finance them together.
"Basically, we have to close the account, and it is no more and no less. No punishment. There is no Brexit bill."
Mr Barnier said the financial settlement must be decided as part of the first phase of negotiations, along with the status of expatriate citizens and the future border between the UK and EU in Ireland.
"The UK must put a great deal of energy and effort into these three issues over the next weeks and months and that will increase the chances of making a deal," he said as he warned of haste on the British side.
"Some have created the illusion that Brexit would have no material impact on our lives or that negotiations can be concluded quickly and painlessly. This is not the case," Mr Barnier added.
"We need sound solutions, we need legal precision and this will take time."
Mr Davis earlier told Good Morning Britain reports Prime Minister Theresa May would be barred from negotiating with her counterparts were "laughable".
Speculation emerged claiming Brussels wants to limit Mrs May's Brexit discussions to direct meetings with Brexit negotiator Mr Barnier.
Mr Davis said the prime minister would retain the right, as she has pledged, to attend Brexit discussions at future EU heads of government meetings while the UK remained a member state.
"The decisions in this exercise at the end of the day are taken at Council - that's a gathering of all the leaders of the European Union - and, frankly, until the day we leave, we are full members of the Union, we have every right to attend every Council and we will exercise our right," he said.
"Just as we are obeying the laws of the Union, exactly to the letter, we are also going to expect our rights," he added.
"The idea that somehow one side of the negotiation can dictate how the other side runs a negotiation is laughable. This is an exercise in trying to shape public opinion and trying to pressurise us - it won't work."
The speculation gathered pace followed reportedly combative talks as the prime minister hosted European Commission President Jean-Claude Juncker in London last week.
The European Parliament's chief Brexit co-ordinator though has said he was "not much worried" about the current escalation of tensions between the UK and EU sides.
"I'm not so surprised by what is happening," Guy Verhofstadt told MEPs. "It always happens before the start of a negotiation. It is the building up of pressure from both sides, let's be honest.
"That will not change until the June 9 date that the negotiations can really start. This building up of pressure I have seen tens and tens of times in other negotiations."