The UK will not pay a €100bn (£85bn) “divorce bill” to leave the EU, Brexit Secretary David Davis has insisted.
He told ITV’s GMB programme the UK would pay what it was legally obliged to do “not just what the EU wants”.
It comes amid claims by the Financial Times that the financial settlement sought by the EU has risen from €60bn.
Mr Davis said the UK treated its EU “rights and obligations” seriously but it had “not seen any number”, adding the EU was playing “rough and tough”.
The EU’s chief negotiator Michael Barnier is due to publish his guidelines for the talks later.
An EU source has told the BBC that officials in Brussels will not enter into a discussion about potential figures for a final bill.
Talks over the size of the so-called “divorce bill” are likely to be one of the hardest-fought and most sensitive areas of the Brexit process.
Mr Davis said the negotiations had not started in earnest but indicated the UK would set down a marker when it came to talks over the divorce settlement.
“We are not supplicants,” he said. “They lay down what they want and we lay down what we want.”
The EU has insisted that the UK will have to accept liabilities stemming from its membership, including contributions to the EU Budget.
The EU has already listed some sort of agreement on a payment from the UK as a precondition for opening talks on a trade deal.
Previous calculations had placed the financial settlement likely to be demanded by the EU at between 50 and 60bn euros.
The Financial Times, using the same economic model with new data from around Europe, suggests that has now gone up to 100bn euros.
There are reports in Brussels that the difference might include demands from countries like France and Poland for UK contributions to farm subsidies.
The EU may also be planning to refuse to allow the UK a share of the EU’s assets including buildings and bank deposits.
The suggestion that the payment would be made in installments would not do much to soften the blow from the British perspective, he added.
The revelation comes amid growing tensions between the UK and EU following reports of a dinner in Downing Street last week, in which European Commission President Jean-Claude Juncker is said to have told Theresa May that Brexit could not be a success.
On Tuesday, Mrs May said Mr Juncker would discover that she could be a “bloody difficult woman”.
Many Conservative MPs argue the UK does not owe the EU anything given the size of the contributions it has made in the past.
A recent report by a House of Lords committee argued the UK was not legally obliged to pay a penny.