The nasty side of Boris Johnson as he makes throat slitting gesture during interview

The Prime Minister was trying to kill a line of questioning but didn't realise he was being filmed during radio interview

Boris Johnson was caught on camera appearing to give a secret signal to stop difficult questions during an interview.

The Prime Minister was fielding questions from the public and from radio host Nick Ferrari on the LBC station this morning.

He didn't seem to appear to realised that the interview was being streamed live and at one point he could be seen making a secret sign to the host to stop the interview when the questioning turned to social care.

The Conservatives have been criticised heavily for failing to address the growing crisis in social care in their election manifesto.

And when Mr Johnson was asked to answer about this subject today he gave a waffly answer before making a throat cutting gesture towards Mr Ferrari.

The host appeared to heed the warning by quickly moving on to a different subject following the Prime Minister's gesture.

During the interview the Prime Minister had to defend disparaging remarks he made about single mothers, telling a voter they were made before he was "even in politics".

An article written by the Conservative Party leader for the Spectator magazine in 1995 has been unearthed in which he described the children of single mothers as "ill-raised, ignorant, aggressive and illegitimate".

In the column, the Prime Minister said it was "outrageous" that married couples "should pay for 'the single mothers' desire to procreate independently of men".

During a phone-in on LBC radio on Friday, Mr Johnson was put to task over the comments by a single mother named Ruth from Oldham.

She told the PM she was unhappy about the content of the article and questioned why he was reluctant to talk about his own family.

Mr Johnson said: "Ruth, I want to say to you, I mean absolutely no disrespect to you or anybody.

"These are 25-year-old quotations culled from articles written I think before I was even in politics."

He said the quotes were stripped of context and formed part of a smear campaign by Labour.

"They're just trying to distract from the reality that they have no plan to get out of the EU."

During the call-in, Mr Johnson also:

• Gave a "guarantee" to take Britain out of the European Union by January 31 if he secures a "workable" majority.
• Said the £58 billion compensation for Waspi women promised by Labour was "a lot of money".
• Confirmed he would "walk out" of trade talks with the US if President Donald Trump wanted the NHS to be on the table.
• Told voters he wanted to come back with a "better answer" to the social care funding crisis - but said the politics had to be taken "out of this".
• Refused to discuss how many children he had fathered, telling LBC: "I love my children very much but they're not standing at this election."
• Admitted his new nurses pledge amounted to 31,000 extra nurses in the NHS - not 50,000.

A video of the Prime Minister's gesture is now being shared widely on social media.