International Trade Secretary Liam Fox | Tolga Akmen/AFP via Getty Images Liam Fox warns ‘Brexit bill’ needs Euroskeptic agreement Reports Theresa May is preparing to accept a figure of up to £50B are ‘complete nonsense.’

LONDON — Any deal between the U.K. and Brussels over Britain's multibillion pound “Brexit bill” will have to be signed off by leading Euroskeptics on Theresa May's all-powerful Brexit cabinet committee, International Trade Secretary Liam Fox said Sunday night.

Fox told POLITICO in an exclusive interview for London Playbook that reports the prime minister was preparing to accept a figure of up to £50 billion were “nonsense,” insisting there had yet to be any official — or private — discussion about the bill at Cabinet level.

“The idea that we have internally or otherwise agreed a figure is nonsense,” Fox said. “It’s complete nonsense. We will examine line by line the arguments the EU puts forward, but neither internally, nor at any point privately, has anyone agreed to such a figure. This story is nonsense.”

The international trade secretary said any deal on money would have to be agreed by the 13-strong cabinet sub committee on exiting the European Union, chaired by the prime minister. Alongside Fox, Johnson and Davis, other prominent government Euroskeptics on the committee include Chris Grayling, Michael Gove and Priti Patel.

Fox said: “Once DExEU [Department for Exiting the European Union] have done their work on this, we would want to discuss it and we have had no such discussion and there has been no such agreement.”

The intervention highlights the political sensitivity around the looming settlement of Britain’s financial obligations to the EU, which is now the major stumbling block to progress in the exit negotiations.

Fox also hit out at the Labour Party’s call for transitional membership of the single market and customs union, insisting the shape of any temporary agreement was impossible to negotiate before a final deal had been agreed.

His position is considerably harder than that of some of his cabinet colleagues, who believe a negotiated transitional deal is now the most pressing issue for the U.K. economy.

He also took aim at colleagues for leaking to the press. “This is an important part of our negotiations and we should be discussing that through the appropriate structures in government and not on the front pages of newspapers.”

Fox was also scathing of Labour’s new position on the transitional membership of the single market and customs union. “The transitional deal will depend on what the final deal looks like,” he said. “I hear the Labour party say this is what we’ll have in the transitional deal. How can you know that? You don’t know what they are transitioning to. Until you know what the end state will look like it’s impossible to say what your transitional deal will look like.

“How people like Keir Starmer can say this is definitely what our transitional deal will look like … how do you know?"

Fox said he had no regrets about backing Leave in the EU referendum.

“After a year here I’m [more] sure that I was right to have voted to leave the European Union than on the day I voted for it," Fox said.