International Trade Secretary Liam Fox has dismissed a claim the UK will be able to continue trading with the EU tariff-free for 10 years.

Boris Johnson has been slapped down by International Trade Secretary Liam Fox over his claim Britain could use international trade rules to continue tariff-free trade with the EU in the event of a no-deal Brexit.

Mr Johnson has argued that a provision under the General Agreement on Tariffs and Trade – known as Gatt 24 – could be used to avoid tariffs under World Trade Organisation (WTO) rules for up to 10 years.

But Dr Fox, a Brexiteer who is backing Jeremy Hunt for the Tory leadership, said that would require the agreement of the EU, which Brussels had made clear would not be forthcoming.

He said it was essential that the public debate on the issue was conducted “on the basis of fact rather than supposition”.

His warning came after a day in which Mr Johnson sought to get his campaign back on track with a media blitz in which he vowed to take Britain out of the EU by the end of October “do or die”.

However, he continued to refuse to answer questions about his personal life following a late-night row last week with his partner, Carrie Symonds, which saw police called to their South London home.

With the contest becoming increasingly heated, Dr Fox posted an article on LinkedIn rebutting Mr Johnson’s claim that Gatt 24 could be used to avoid a disorderly Brexit.

“A ‘no deal’ scenario, by definition, suggests that there would be no mutual agreement between the UK and the EU on any temporary or permanent arrangement. In those circumstances Article 24 cannot be used,” he said.

“The European Union has made it clear on a number of occasions that full tariffs will be applied to the United Kingdom in the event of ‘no-deal’.”

He added pointedly: “It is important that public debate on this topic is conducted on the basis of fact rather than supposition, so that we are able to make decisions in the best interests of our country.”

His comments echoed the Bank of England Governor Mark Carney who said that without an agreement with the EU, WTO tariffs would apply “automatically” in the event of no-deal.

In an interview with LBC on Tuesday, Mr Johnson insisted Gatt 24 did offer a possible “way forward” but accepted that Mr Carney was right to say it required “mutuality”.

“Where Mark is right, is saying that implies mutuality. There has to be an agreement on both sides,” he said.

“But he’s wrong in thinking it’s not an option. It certainly is an option, people are wrong if they say it’s not an option.”

The two remaining contenders to succeed Theresa May will face more questions on Wednesday in a digital hustings.

Mr Johnson used a series of broadcast interviews on Tuesday to set out his plans for Brexit, insisting that the shock of the European election results would force both the Tories and Labour to acknowledge that the current impasse could not continue.

He also challenged Mr Hunt, the Foreign Secretary, to match his commitment to deliver Brexit by the deadline of October 31, with or without a deal with the EU.

Mr Hunt dismissed October 31 as a “fake deadline” which – if adhered to – could lead to a general election which would hand power to Labour and derail Brexit altogether.

In a BBC interview he suggested Mr Johnson would find it difficult to get a new deal with Brussels as he would struggle to win the trust of fellow EU leaders.

“The judgment is who is the person we trust as prime minister to go to Brussels and bring back that deal,” he said.

“It’s about the personality of our prime minister. If you choose someone where there’s no trust, there’s going to be no negotiation, no deal.”

During a question and answer session on Twitter, Mr Hunt said he believed cuts to the police had gone “too far”.

“Can’t commit today to fully reversing those cuts but I will look into it,” he said.

In response to a question as to whether he was “Theresa May in trousers”, he joked: “Never fancied leather trousers myself.”

By Gavin Cordon, Press Association Whitehall Editor.