Tory leadership rivals Boris Johnson and Jeremy Hunt clash over Brexit plans

Boris Johnson and Jeremy Hunt have clashed over their plans for delivering Brexit as a former head of the civil service warned against making “straitjacket” promises to leave on Halloween.

In an open letter, Mr Johnson challenged his rival to commit to taking Britain out of the EU on October 31 “come what may”, warning not doing so would have “devastating” consequences for the Conservative Party and the country.

However, Mr Hunt hit back, calling it a “fake deadline” which – if adhered to – could lead to a general election which would hand power to Labour and derail Brexit altogether.

Mr Johnson’s apparent hardening of his stance on guaranteeing Brexit “with or without a deal” came as former civil service chief Bob Kerslake called the October 31 pledge “a complete hostage to fortune”.

In comments reported by The Independent, the former Whitehall mandarin warned Parliament will not countenance leaving the EU without a deal.

“It is always a good maxim in politics not to enter a room unless you know that you can get out of it,” the peer told the Chamberlain lecture in London on Tuesday.

“Boris Johnson has not only entered the room but he has put on the straitjacket, padlocked the door and started the tap running.”

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.

In a BBC interview, Mr Hunt 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.”

Mr Hunt has pledged to leave no deal on the table as an option, but has left open the potential for a short extension if an agreement with Brussels is in reach.

“I think that 31 October come hell or high water is a fake deadline, because it’s more likely to trip us into a general election before we’ve delivered Brexit, and that would hand the keys to Jeremy Corbyn and then we’d have no Brexit at all,” he told the BBC.

“I will leave the European Union without a deal. But I’m not going to do that if there’s a prospect of a better deal and if I did it it would be with a heavy heart because businesses up and down the country would face a lot of destruction.”

Mr Johnson’s Brexit plans also came under attack from International Trade Secretary Liam Fox, who slapped down the former foreign secretary over his claim Britain could use international trade rules to continue tariff-free trade with the EU in the event of no-deal.

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 Mr 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”.

Dr Fox’s 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.

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