Boris Johnson is a “zombie prime minister” who must leave office, according to the SNP’s Westminster leader Ian Blackford.

Opposition politicians have been calling for Mr Johnson to resign after the UK’s highest court on Tuesday ruled that his suspension of Parliament was unlawful.

MPs will return to Westminster on Wednesday following the court’s finding that the five-week prorogation was “void and of no effect”.

Speaking on the BBC’s Good Morning Scotland programme, Mr Blackford said Mr Johnson must be held account.

“This is unprecedented in our parliamentary history,” said Mr Blackford.

“The Government is trying to brush this off as just an inconvenience, it simply isn’t good enough.

“He has shut down Parliament in a manner which is unlawful and he needs to be held to account for that. They really have to accept responsibility as to why they have behaved in a manner which is unlawful.

“When you put this into a broader context that this is a zombie Prime Minister, a zombie Government, doesn’t have a majority, he’s lost six votes in the short time that he’s been Prime Minister – he needs to go. We need to have a general election.”

Ian Blackford leaving the Supreme Court
Ian Blackford leaving the Supreme Court (Jonathan Brady/PA)

Asked about Mr Johnson’s attempts to hold an early general election, the SNP Westminster leader described it as a “poisoned chalice”.

“There is an opportunity for the opposition to come together to recognise this is a Government that’s run its course, a Prime Minister that doesn’t have a mandate and we should be ending his tenure in 10 Downing Street.

“We need to make sure we can remove him but in a manner which is safe, and we can do that by having a motion of no confidence where we can seize the initiative and we can move quickly to have an election, safe in the knowledge that the extension to the Article 50 process is going to be granted.

“I want the people of Scotland to be able to reject this Tory Government and for us to be able to take responsibility for our own future and to send a very clear message to Westminster.”

Also appearing on the programme, Scottish Conservative MSP Adam Tomkins described the Supreme Court verdict as a “stunning judgment”, but said it was important to “dispense with myths” that the Prime Minister had lied to the Queen.

“The prorogation has been ruled unlawful, let’s leave it at that,” said Prof Tomkins.

“Parliament will reconvene this morning and the Prime Minister will no doubt face questions from MPs during the course of the day.

“It’s a stunning judgment and we’re not trying to downplay its significance, but let’s just dispense with myths. The Prime Minister’s not lied to the Queen, that’s not what the Supreme Court’s said yesterday.

“The Prime Minister continues in office for as long as he or she enjoys the confidence of the House of Commons.

“If the leader of the opposition really thinks Boris Johnson does not have the confidence of the House of Commons then he should today lay down a motion of no confidence in Boris Johnson’s administration and if he wins that there’ll be an early general election.”

Asked if he had confidence in Mr Johnson as Prime Minister, the MSP added: “Frankly it doesn’t matter whether he has my confidence.”