Boris Johnson has been branded a threat to national security by cabinet allies of Tory leadership rival Jeremy Hunt.

Ministers claimed last night that Mr Johnson's volatile private life left him open to manipulation and even blackmail by foreign powers.

The astonishing attack comes after Mr Hunt launched a stinging assault on his rival, questioning his character.

Mr Hunt's supporters went a step further, with a senior cabinet minister describing Mr Johnson as a security risk.

Allies of Jeremy Hunt (pictured taking part in a Conservative Party leadership hustings event in Birmingham yesterday) questioned whether his leadership rival Boris Johnson's personal life posed a threat to national security

He made the comments in conversation with another cabinet minister, who told the Sunday Times: 'There will be things in his private life that we don't know about.

'There's the danger that people leak what they have over him or blackmail him with it.'

Earlier, Mr Hunt criticised the 'populist' Mr Johnson - insisting Britain needs a PM who keep their promises.

The Foreign Secretary sought to turn the screw on his opponent after it emerged the police was called to a blazing row between Mr Johnson and his 31-year-old girlfriend at her flat in Camberwell.

Without referring to the episode, Mr Hunt left no room for doubt that he wants the contest to be about character.

In an open letter, he called on his rival to stop dodging questions and said: 'The purpose of this stage is to test us - our plans, our policies, our character.

'Scrutiny can be uncomfortable. But if we can't handle it with friends, we won't deserve to lead against our opponents.'

Boris Johnson (speaking at a Conservative Party leadership hustings event in Birmingham) was described as being open to blackmail from foreign powers by allies of Mr Hunt

The claims come after police were called to the flat Mr Johnson shares with girlfriend Carrie Symonds (pictured), with neighbours describing a blazing row between the couple

He also urged him to get involved in more public debates ahead of ballot papers being sent out on July 5.

Mr Hunt slammed Mr Johnson for only having committed to a television debate on July 9, after many Tory members were like to have cast their vote.

He said: 'I'm concerned that you have only so far committed to one TV debate - the ITV debate on July 9, which is after members will have started to return their postal ballots.

'So my challenge to you is this: let's have live televised debates right at the start of this contest, and specifically at least two in the next two weeks before members receive their ballot papers.

'To date, I have accepted live televised debate invitations from Sky, the BBC, Channel 4, the Sun and ITV. My message is simple: if you want the job, you have to turn up for the interviews.'

Also today, Mr Hunt released a open letter (pictured) to Mr Johnson urging him to get involved in more public debates ahead of ballot papers being sent out on July 5

He said activists had to ask themselves who they 'trust' to negotiate a deal with the EU, suggesting that Mr Johnson's plans were not realistic. He insisted part of the problem over the past three years was that politicians made promises they could not keep.

And in a vicious swipe he warned that Mr Johnson could plunge the Tories into the same chaos and misery as Jeremy Corbyn did to Labour.

'We could choose our own populist - or we could do better, and choose our own Jeremy,' he said.

But despite their war of words the rivals felt friendly enough to drape an arm around each other after the event.

Jeremy Hunt (pictured yesterday) sought to turn the screw on his opponent after it emerged the police were called to a blazing row between Boris Johnson and his 31-year-old girlfriend

Earlier, Mr Johnson flatly refused to answer questions about the explosive row with his girlfriend as he ran the gauntlet of the first Tory leadership hustings

Earlier, Mr Johnson flatly refused to answer questions about the explosive row with his girlfriend as he ran the gauntlet of the first Tory leadership hustings.

Speaking at a hustings in Birmingham, Mr Johnson did not mention the issue in his opening comments, insisting: 'We need to get Brexit done... and I am the right man.'

And repeatedly challenged by broadcaster Iain Dale on stage, he replied: 'I don't think people want to hear about that kind of thing.'

Mr Johnson admitted the public was 'entitled to know about my determination and character'. But he added: 'Let me tell you that when I make a promise in politics about what I want to do I keep that promise.'

The dead bat response drew cheers from the audience - who also started booing when Dale tried to push further.

Mr Hunt insisted a 'wise PM' would make choices on the basis of the options that are 'actually available'.

And he warned that Mr Johnson was making promises he could not keep.

'Now we don't know what the situation will be on the 31 October, but if there is no prospect of a better deal, if the European Union have been as inflexible as you say, and if no deal is on the table, then I will leave without a deal because we must keep our promise to the British people,' he said.

Hunt insists he DOES feel Brexit 'in my gut' Jeremy Hunt insisted he feels Brexit 'in my gut' as he came under pressure from Tory activists today. The Foreign Secretary faced claims of flip-flopping by backing Remainer in the referendum, before claiming to be a convert to the cause. But in a swipe at Boris Johnson, who failed to vote for Theresa May's Brexit deal in two out of three key divisionsm Mr Hunt said: 'At every stage where I could support Brexit I have voted for it.' And he pleaded with activists to move on from the divisions of the past three years. 'If we carry on three years after the Referendum labelling people as Remainer Remainer Brexiteer Remainer Brexiteer we're not going to unite our party, and we're not going to get this vote through the House of Commons. 'We've got to come together and deliver Brexit.' He added: 'This language is so destructive because we are going to need a coalition inside the Conservative Party.' Advertisement

'But I would do so with a heavy heart, because of the risks to businesses up and down the country and the risks to the union.

'But if we have to, in the end I would do that. But the reason that I haven't made the pledge that Boris has made is because I think it's very important that prime ministers keep their word.

'It is entirely possible that Parliament will rule out no-deal between now and 31 October.'

Mr Hunt urged activists to consider: 'Who is the PM we trust to send to Brussels and lead us out of this crisis?

'Send the right person and there's a deal to be done.'

But he said , 'catastrophe awaits' if they make the wrong choice.

'If we send the wrong person there's going to be no negotiation, no trust, no deal, and if Parliament stops that, maybe no Brexit,' he said.

Mr Hunt also had a dig at Mr Johnson for failing to back Theresa May's Brexit deal in two of the three 'meaningful' votes.

'At every stage where I could support Brexit I have voted for it,' Mr Hunt said.

Mr Johnson and his girlfriend were recorded by neighbours having a 'plate-smashing, screaming row' during which Miss Symonds demanded he leave. Police were called, but no formal action was taken.

In the wake of the controversy Miss Symonds 'liked' a tweet stating 'we must have have entertainment at number 10' - seemingly making light of the extraordinary incident.

But she was nowhere to be seen at the hustings this afternoon, despite attending his campaign launch earlier this month.

Mr Johnson rejected claims he has been softening his position that Britain must leave the bloc by the end of October, deal or no deal.

Without referring to the episode, Mr Hunt left no room for doubt that he wants the contest to be about character

Mr Hunt jibed at the hustings: 'We could choose our own populist - or we could do better, and choose our own Jeremy.'

Mr Johnson also doubled down on his claim that the UK would be able to waive tariffs on EU goods even if there is No Deal. Bank of England governor Mark Carney dismissed the idea yesterday, as has Trade Secretary Liam Fox.

But senior Tories mocked him during the speech by posting images of unicorns on Twitter. And one Tory member at the event turned the air blue by condemning his 'f*** business' jibe about companies raising concerns about hard Brexit.

Mr Johnson said the swipe had been 'one stray remark to the Belgian ambassador' during a private reception.

He said his record was 'pretty extraordinary' when it came to supporting business, even defending bankers after the 2008 financial crunch.

He also refused to rule out cancelling the HS2 rail project, or taking direct action to stop the expansion of Heathrow Airport. Asked about his previous pledge to 'lie down in front of the bulldozers', Mr Johnson said: 'We'll have to see when the bulldozers appear.'