BORIS Johnson should resign if he lies to parliament, his Scottish leader has said.

Jackson Carlaw said deliberately misleading parliament should be the end of any political career during the BBC Scotland leaders’ debate last night.

With trust a key issue in the election and the Prime Minister having a track record of untruthfulness in his journalistic career and private life, the remark was a clear hostage to fortune for the Tories.

It coincided with a new YouGov poll for the Times suggesting Mr Johnson will be returned as Prime Minister on Thursday with a narrow majority.

On the BBC debate, the Scottish party leaders were asked whether it should be a criminal offence for politicians to lie to parliament.

Mr Carlaw said: “It should be a resignation matter. If people say something quite deliberately - I mean, you inadvertently give the wrong answer - but if they say something that’s deliberately wrong that should be a resignation matter.” 

Ms Sturgeon said the “long and short of it” should be lying was something that politicians should not do.

She said: “We shouldn’t deliberately mislead people. One of the really troubling things about politics in the UK right now is that we have a candidate for Prime Minister who seems to lie with impunity and do it repeatedly, and I think that is deeply, deeply concerning.”

Scottish Liberal Democrat leader Willie Rennie also said it should not be a criminal offence, but added: “What we do need is greater integrity in politics. Boris Johnson isn’t fit to be the Prime Minister of this country. He lies repeatedly.

“It’s important we try and raise the standard of the debate in this country and you will not get that with Boris Johnson.”

Mr Carlaw also distanced himself from the Prime Minister’s record in last week’s STV leaders debate, when he said some of his past comments about Muslim women and gay men were “absolutely unacceptable”.

Scottish Labour leader Richard Leonard said that with prisons already overcrowded, a civil offence might be more appropriate.

Mr Carlaw also savaged Ms Sturgeon for failing to abide by her “once in a generation” promise on an independence referendum.

Mr Carlaw said: “Nicola Sturgeon doesn’t accept the outcome of referendums. She’s already said if she didn’t win a second referendum on Brexit she wouldn’t accept it.

“Does anybody here believe if she lost a second independence referendum she wouldn’t then start a campaign for a third?

“My argument would be that we’ve spent all this time and division talking about the constitution. What powers does the Scottish Parliament have? It has powers over education, it has powers over health, powers over justice, powers over our economy.

“It’s those public services that are currently suffering because Nicola Sturgeon’s first, second, third and fourth priority is the constitution.

“Not your jobs, not your health service, not your schools, and not the Scottish economy. That’s what we need to concentrate on.”

Ms Sturgeon replied: “This nonsense about not accepting referendums - the 2014 referendum went against me. Scotland is not independent.”

Mr Carlaw interjected: “You’ve never accepted it.”

She replied: “I accepted that. I don’t accept the result of the Brexit referendum because Scotland voted to remain, and as First Minister of Scotland I think I’ve got a duty to represent that majority opinion.

“But in a democracy, Jackson, people have the right to change their minds.”

Mr Carlaw said he was respecting her once in a generation commitment from 2014.

Earlier,  a Glasgow Tory MSP disowned Mr Johnson over his unsympathetic reaction to a sick child forced to lie on a hospital floor.

Annie Wells said she did not “represent Boris Johnson”, despite him being her party’s ultimate leader.

In the warm-up show before the debate, Ms Wells was asked about the Prime Minister’s refusal to even look at a picture of the four-year-old boy in Leeds.

Mr Johnson was accused of having an “empathy bypass” after pocketing the phone of ITV reporter Joe Pike when he tried to show him the picture on Monday.

Asked about the incident before the BBC Scotland leaders’ debate, Ms Wells said: “I will admit that he could have done better. I wouldn’t have handled it that way.

“But I don’t represent Boris Johnson. I don’t understand his way of thinking. But what I would say is that it is one thing in this campaign and he could have handled it better.”

It followed SNP Brexit Secretary Michael Russell telling the same programme the incident was further proof that Mr Johnson was “unfit” to remain in Downing Street.

The debate also touched on poverty, taxes and the welfare system.

The Scottish Tories urged Ms Sturgeon to rule out more Scottish income tax rises if national insurance was cut for the poorest.

At one point, Mr Rennie was reprimanded by one female audience when he tried to question Nicola Sturgeon about the currency in an independent Scotland.

She said: “Can I ask Willie Rennie to stop talking over people? It’s really rude.”