Business leaders are unable to plan properly for potentially huge disruption from Brexit because of excessive government secrecy, the chief auditor says.

Companies have paid a “heavy price” for ministers’ refusal to consult them fully, an inquiry by MPs was told – a stance motivated by a fear of provoking concern about the trouble ahead.

The criticism came as the head of the National Audit Office (NAO) revealed that civil servants are relying on his reports to find out what is going on in their own departments.

Sir Amyas Morse also agreed there was a real risk that flights to the EU would be grounded if there is no-deal Brexit, warning the UK was relying on “goodwill” to resolve the crucial issue.

And he suggested Theresa May’s planned 21-month transition period, after departure day next March, would be too short to secure long-term arrangements – which would require the transition to be extended.

The NAO’s auditor general also dismissed claims that crashing out of the EU onto World Trade Organisation (WTO) rules would be a comfortable outcome, warning of “high friction” for traders.

And he criticised the department for transport for underestimating the risks of Brexit, saying they had “convinced themselves it is less risky than it actually is”.

Giving evidence to the Commons Brexit committee, Sir Amyas said the secrecy surrounding preparations had been “taken too far” – particularly for businesses.

Boris Johnson 'suicide vest' Brexit jibe causes Tory divide Show all 14 1 /14 Boris Johnson 'suicide vest' Brexit jibe causes Tory divide Boris Johnson 'suicide vest' Brexit jibe causes Tory divide Internal divisions in the Conservative Party have exploded into a bitter public row over Boris Johnson‘s “disgusting” criticism of Theresa May. Some senior Tories furiously denounced the former foreign secretary after he accused the prime minister of having ”wrapped a suicide vest” around Britain Reuters Boris Johnson 'suicide vest' Brexit jibe causes Tory divide Sajid Javid, Home secretary Sajid Javid, the home secretary, rebuked his former cabinet colleague and said: “I think there are much better ways to articulate your differences.” He told the BBC’s Andrew Marr Show that the public wanted politicians to use “measured language” BBC/PA Boris Johnson 'suicide vest' Brexit jibe causes Tory divide But other MPs leapt to Mr Johnson’s defence, as dividing lines ahead of a possible leadership contest begin to take shape. The Uxbridge MP has repeatedly criticised Ms May’s Chequers plan and used a newspaper article on Sunday to suggest it amounted to “wrapping a suicide vest around the British constitution”. His latest salvo at the prime minister prompted immediate condemnation, with one minister publicly vowing to end Mr Johnson’s career over the matter PA Boris Johnson 'suicide vest' Brexit jibe causes Tory divide Alan Duncan, Foreign minister Alan Duncan, a foreign minister who worked in Mr Johnson’s team for two years, wrote on Twitter: “For Boris to say the PM’s view is like that of a suicide bomber is too much. This marks one of the most disgusting moments in modern British politics. “I’m sorry, but this is the political end of Boris Johnson. If it isn’t now, I will make sure it is later.” Getty Boris Johnson 'suicide vest' Brexit jibe causes Tory divide James Brokenshire, Housing secretary Housing secretary James Brokenshire added his voice to the criticism, calling Mr Johnson’s comments ”wrong” He said: “I think he is wrong on this...I think the tone that he has used isn’t right and I think that we just need to be very focused on actually moving forward with the Chequers plan.” AFP/Getty Boris Johnson 'suicide vest' Brexit jibe causes Tory divide Zac Goldsmith But as Tory hostilities spilled over into open public warfare, Richmond Park MP Zac Goldsmith, an ally of Mr Johnson, hit back at Mr Duncan. He wrote: “There are a number of possible motives behind this tweet, but given its author, we can be certain ‘principles’ aren’t one of them.” Getty Boris Johnson 'suicide vest' Brexit jibe causes Tory divide Jacob Rees-Mogg Senior Tory Brexiteer Jacob Rees-Mogg told The Independent he thought Mr Johnson’s “suicide belt” accusation was little more than “a characteristically colourful catchphrase”. He added: “I agree with the sentiment. The criticism of Boris’s wording merely serves to highlight his point. It means more people hear of Boris’s criticism of Chequers and many will agree with him.” Reuters Boris Johnson 'suicide vest' Brexit jibe causes Tory divide Nadine Dorries Nadine Dorries, another Brexit supporter, said Mr Johnson’s opponents were “terrified of his popular appeal”, adding: “Don’t underestimate the vitriol that’ll be directed towards Boris today. He delivered the Leave vote, Remainers and wannabe future PMs hate him.” If Mr Johnson became leader and prime minister he would deliver a “clean and prosperous” Brexit, she said Rex Boris Johnson 'suicide vest' Brexit jibe causes Tory divide Andrew Bridgen Andrew Bridgen said Ms May was to blame for her leadership problems. Asked if Mr Johnson had put a bomb under her leadership, Mr Bridgen said: “I think that Theresa May did that herself when she put forward the Chequers proposals without consulting widely prior to that.” Boris Johnson 'suicide vest' Brexit jibe causes Tory divide Steve Baker, former Brexit minister Steve Baker, the former Brexit minister, warned Ms May the Conservatives faced a "catastrophic split" if she did not jettison her Chequers plan. Mr Baker, who quit the government in July over the scheme, said: “When negotiating, the prime minister needs to demonstrate her intent and also her power to deliver. "If we come out of conference with her hoping to get Chequers through on the back of Labour votes, I think the EU negotiators would probably understand that if that were done, the Tory party would suffer the catastrophic split which thus far we have managed to avoid.” But he insisted he did not want a change in the Conservative leadership, saying Brexiteers did “not want to be in a position of conflict with our own prime minister” Reuters Boris Johnson 'suicide vest' Brexit jibe causes Tory divide Tom Tugendhat The deep divisions on the Tory benches were laid bare as Tom Tugendhat, who chairs the Commons foreign affairs committee and is a possible leadership rival to Mr Johnson, also hit out at the former foreign secretary. Recalling how he encountered a suicide bomber in Afghanistan during his time in the army, Mr Tugendhat told Mr Johnson to “grow up”. He said: “A suicide bomber murdered many in the courtyard of my office in Helmand. The carnage was disgusting, limbs and flesh hanging from trees and bushes. Brave men who stopped him killing me and others died in horrific pain. “Some need to grow up. Comparing the PM to that isn’t happy.” PA Boris Johnson 'suicide vest' Brexit jibe causes Tory divide Alistair Burt Alistair Burt, another Foreign Office minister who worked in Mr Johnson’s team, said: “I’m stunned at the nature of this attack. There is no justification for such an outrageous, inappropriate and hurtful analogy. “If we don’t stop his extraordinary use of language over Brexit, our country might never heal. Again, I say, enough.” AFP/Getty Boris Johnson 'suicide vest' Brexit jibe causes Tory divide It comes amid that Ms May’s former aides drew up a dossier on Mr Johnson’s sexual encounters with the aim of undermining his leadership prospects. The document was compiled in 2016, when the Uxbridge and South Ruislip MP was seen as the main rival to Ms May in her bid to enter No 10. Downing Street and Conservative Campaign Headquaters (CCHQ) both denied having leaked the 4,000 word memo after it was circulated around Westminster AFP/Getty Boris Johnson 'suicide vest' Brexit jibe causes Tory divide Mr Johnson confirmed that his 25-year marriage to wife Marina had ended AP

He said he understood the “desire to not cause concern”, but warned: “It has carried a heavy price with it.”

The auditor added: “I think they underestimate the capability and maturity of the business community.

“They are actually very good at running their businesses. If you don’t give them a chance to plan ahead and solve the problem you put them in a very difficult position.”

On the effect of secrecy on Whitehall, Sir Amyas said: “Members of the civil service have been using our reports to find out what’s happening on Brexit.

“I don’t think that’s a good state of affairs. I’m thrilled a have a wider readership but, if you ask people to be behind what you are doing, you need to make sure they do know what the overall enterprise is and feel really well informed.”

Dominic Raab, the Brexit secretary, has not challenged industry warnings that a no-deal Brexit would bring delays at Channel ports of “45 mins for just one truck”.

And he has appeared to confirm plans for lorries to be parked for many miles along one side of the key motorway link to Dover, once referring to “contra-flow systems on the M20”.

Later, Sir Simon Fraser, former Foreign Office permanent secretary, reminded the committee that Mr Raab had claimed Brexit would but bureaucracy and regulations.

He pointed out there were already 7,000 more civil servants, preparing for EU withdrawal, with a further 16,000 planned for 2020.