BORIS Johnson was accused of making a “career out of lying” in the House of Commons yesterday, in a heated exchange between Ian Blackford and Theresa May.

Despite it being against the rules to suggest another member has been untruthful – at least without giving them notice first – Speaker John Bercow didn’t object to Blackford’s attack on Johnson, much to the fury of the Tory benches who howled “withdraw”.

In his question to the Prime Minister the SNP MP accused her of showing “gross cowardice”.

“On the one hand, the Tories are asking people to put their faith in the most incompetent Foreign Secretary in a century – a man who has made a career out of lying, and who has spent the week avoiding the media, staging photos and playing to the extreme delusions of the Tory shires,” he added.

“On the other hand, we have the most incompetent Health Secretary in our history, a man who writes books on privatising our NHS.”

He asked May to “finally act in the best interests of these islands” and “admit that neither of the candidates for office should ever be elected Prime Minister”.

The outgoing Tory leader did not agree.

“Either of the candidates for this high office would do a darned sight better job than anybody sitting on the opposition benches,” she shouted.

The Tories behind her shouted “more” as she sat down.

But with just five more weeks left in office, any obligation her backbenchers had to support May at the weekly Commons session has seemingly evaporated with just 99 of her party’s 312 MPs bothering to turn up yesterday.

Later, Tory MP Robert Courts raised Blackford’s comment with Bercow. The Speaker said he had not heard the comment.

Meanwhile, Scottish Tory leader Ruth Davidson has announced she is backing Jeremy Hunt in the leadership contest.

Davidson tweeted: “Any Conservative leadership candidate must put the Union first. Jeremy has done so and will get my vote.”

She first supported Home Secretary Sajid Javid before he was eliminated, before then backing Michael Gove.

When he lost, she admitted that her backing might be the “kiss of death” for anyone vying for the top job.

A majority of Scottish Tories in Holyrood have said they’ll back Hunt, with 18 of the party’s 31 MSPs signing a letter offering the Foreign Secretary their support. Though only three of their 13 MPs have backed Hunt.

In a letter they say they are confident “Jeremy Hunt is the best choice to strengthen the Union, deliver Brexit and move the United Kingdom on with astute policies that will turbo-charge our economy and build the most pro-business environment in Europe”.

The race itself was dominated again by Brexit, and the 31 October deadline.

Johnson has challenged his rival to agree to take the UK out of Europe on Halloween “come what may”.

But Hunt has accused the former Mayor of London of making a vow he can’t keep.

“You should only, if you want to be Prime Minister, make promises you can actually deliver.

“My concern about that fixed date is that we know parliament will try and stop a no-deal Brexit and then you could end up tripping into a general election, that puts Corbyn in Downing Street and there’ll be no Brexit at all.”

Johnson supporter Dominic Raab suggested Downing Street would be able to ignore parliament’s efforts: “If there is a motion passed by MPs which says ‘uh-uh’ [to a no-deal Brexit], it would have zero legal effect.”