BORIS Johnson “knew what he was doing” when he linked Keir Starmer with the failure to prosecute paedophile Jimmy Savile, Nicola Sturgeon has said.

She said either the Prime Minister was “not naïve” and was either “trying to stir up the kind of hate that flows from that, or they don’t care about that being the consequence”.

It comes after the Labour leader had to be rescued by police leaving the Commons on Monday evening.

He was mobbed by protesters who accused him of protecting paedophiles, apparently inspired by the Prime Minister’s slur against Starmer.

READ MORE: Jacob Rees-Mogg becomes 'Minister for Brexit Opportunities'

Johnson chose to “weaponise a conspiracy theory circulated around social media by the far right”, according to the First Minister.

Speaking on Sky News on Tuesday, Sturgeon said this could be either a “dangerous” or “positive” moment for politics in the UK, but that would depend if “responsible politicians come together in the right spirit”.

She added: “Credit to Keir Starmer and to David Lammy, who will know more than most of us about these far right attacks, for the way they conducted themselves.

“I have had some experience personally of being confronted on the streets by the far right, it’s not pleasant, it’s deeply unpleasant, and I’m sure they will have been deeply shaken by it.

“I think they deserve credit for the way in which they handled it.”

She added: “This is a moment to decide that this is not acceptable in our politics.

READ MORE: LibDems in 'foolish and ill-informed' snipe against SNP amid BBC row

“Tough scrutiny of politicians is essential in our democracy but when that crosses the line and becomes the stirring up of hate and abuse, something has gone far wrong and that’s a moment to draw a line in the sand and say we cannot allow this to continue.”

Sturgeon went on to call on the Prime Minister to apologise and withdraw his remarks.

“If he has a shred of decency – and I appreciate that may be the flaw in the argument I’m about to make,” the First Minister said.

“If he has a single shred of decency, he will withdraw the comments that he made completely and he will fully, unreservedly, unequivocally apologise to Keir Starmer and he will join others in saying that we should hold each other to account, we should have robust debate in a democracy, but we should all draw the line at bringing the smear and the lies and the conspiracy theories of the far right and the other trolls that populate social media into the mainstream of our democracy.”