Boris Johnson is not fit to be prime minister because of his “unstable” political views and private life, Labour’s John McDonnell has suggested.
The shadow chancellor said that the unpredictable nature of Johnson’s character meant that even Tory MPs were worried about what he would do in office.
The broadside at the Tory leadership contender came as Labour stepped up its attack on anonymous briefings about Jeremy Corbyn’s own fitness for No.10.
Johnson has steadfastly refused to comment about a heated row he had with girlfriend Carrie Symonds last month.
But McDonnell suggested that the former foreign secretary had proved himself too unpredictable to take over as PM.
“I actually think the instability of Boris Johnson himself in terms of - well, in all aspects of his life – the unstable nature of Boris Johnson and his political decision making, anything could happen,” he told reporters.
“I think that’s one of the deepest worries that all of us must have for the future of the country and the economy – and that includes I think many Conservative MPs.”
Johnson has been accused by some Tory MPs of changing his mind on Brexit ahead of the 2016 EU referendum, and has in recent days shifted his position on issues like tax policy, Heathrow and public sector pay.
Asked if Brexit could no longer happen, McDonnell replied: “I think anything can happen now. I think it’s just almost impossible to tell what will happen in September, October.”
In a separate move, Corbyn wrote to cabinet secretary Sir Mark Sedwill to demand an independent investigation into a Times report that senior civil servants had gossiped about his physical health and capacity to be PM.
Downing Street revealed that a Cabinet Office investigation had been launched into whether senior civil servants had claimed that Corbyn was “too frail” to be prime minister.
Theresa May’s official spokesman said: “The Cabinet Office is investigating this potential breach of the civil service code fully and fairly just as it would any other. If we are able to identify an individual responsible we will take disciplinary action.”
Shadow cabinet office minister Laura Pidcock told BBC Radio 4′s Today programme that the claims about Corbyn’s health were “ridiculous”
“He’s much fitter than me – and I’m 31. It’s ridiculous. The reason many of us in the Labour Party find this so absurd is because everybody knows from seeing him around Westminster, from his schedule, from his personal life he is just really really fit and well,” she said.
“We have to look at the underlying motivations behind those comments. We are talking about some of the most senior civil servants here...If they are against [Labour’s radical] agenda perhaps it is all part and parcel of sowing doubts in the kinds of people out there that Jeremy is up to it.”
One Tory source pointed out that both Johnson and Hunt had condemned the civil service gossip about Corbyn’s health, adding a full investigation was needed.
A source close to Johnson hit back at McDonnell’s remarks. “Jeremy Corbyn and his Marxist-loving acolytes are turning to personal attacks because they know a Conservative party led by Boris Johnson would condemn them to the dustbin of history,” they told HuffPost UK.
“This is only because Boris is committed to delivering Brexit on October 31, with or without a deal.”
Meanwhile, McDonnell revealed that he had asked Jeremy Corbyn to raise with cabinet secretary Mark Sedwill the idea of opening up talks with the civil service to discuss Labour’s detailed plans for government in the event of a snap election – including plans for a second Brexit referendum.
“Jeremy has made it clear that it should go back to the people in a referendum. And we’d expect just as you’d expect the civil service to prepare for an incoming government, for them to prepare for all options so yes that would have to be an option.
“The big mistake that David Cameron made was to prevent the civil service do any preparations for the outcome of the referendum that he didn’t want. Lessons have been learned from that.”