Jeremy Corbyn has accused Boris Johnson of stooping to name calling after the Foreign Secretary claimed he was a threat to national security and a “mutton-headed old mugwump”.

The Labour leader said that the Conservatives had already been reduced to personal insults, just over a week into the election campaign.

The Tories have spent the last five days highlighting Mr Corbyn’s views on defence issues, including his opposition to the Trident nuclear deterrent.

In their last Commons head-to-head on Wednesday Prime Minister Theresa May also referred to a pro-Corbyn website which attempts to address voter concerns that he is a "terrorist sympathiser", because of comments he made in the past describing Hamas and Hezbollah as "friends".

Mr Johnson said that he questioned how Mr Corbyn would respond to the "semi-deranged" regime in North Korea.

The Foreign Secretary also claimed that the UK would be "totally stiffed" in Brexit talks if Mr Corbyn was negotiating with Brussels.

Writing in the Sun, Mr Johnson said: "The biggest risk with Jeremy Corbyn is that people just don't get what a threat he really is."

He added: "They watch his meandering and nonsensical questions and they feel a terrible twinge of human compassion. Well, they say to themselves: he may be a mutton-headed old mugwump, but he is probably harmless."

"It is absolutely vital for Britain's security that we have the strong, stable and decisive leadership of Theresa May."

Shadow cabinet minister John Healey accused Mr Johnson of attention-seeking.

"I think this is Boris Johnson feeling left out of the election campaign,” he said.

“It's the sort of look-at-me name calling that you would expect in an Eton playground”.

Earlier this week it was reported that some in the Tory campaign wanted to sideline Mr Johnson for the duration of the election.

The one-time popular mayor of London has become a hate figure for pro-Remain voters after spearheading the campaign to leave the EU.

Visiting Harlow in Essex, Mr Corbyn said: "We're eight days into the election campaign and the Tories have reduced to personal name calling. I've never been involved in that and never will be.

"We're in this election because we have a serious debate to be held on all the issues facing this country - such as housing, schools, health, what we're talking about today - but also how we deal with the major issues around the world.”

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