Downing Street was accused of a “disgraceful slur on judicial independence” on Wednesday after sources briefed journalists that Scottish courts were biased. 

Boris Johnson’s decision to prorogue parliament was ruled unlawful by a panel of judges at the Court of Session in another blow to the prime minister’s authority.

N0. 10 sources accused Scottish courts of being politically biased, telling The Sun: “We note that last week the High Court in London did not rule that prorogation was unlawful. The legal activists choose the Scottish courts for a reason.” 

Johnson’s official spokesman later made clear the PM had “total confidence” in British judges.

Justice Secretary Robert Buckland, who is a member of Johnson’s cabinet, also made his position clear. 

He said: “Our judges are renowned around the world for their excellence and impartiality and I have total confidence in their independence in every case.” 

But the earlier briefing sparked widespread anger among those who said Downing Street unfairly attacked judges. 

SNP MP Joanna Cherry said it was a “disgraceful slur on judicial independence”,

Cherry said that she and the other campaigners behind the case chose the Court of Session as England’s High Court was not sitting in August. 

Ex-justice secretary David Gauke, who was thrown out of the party when he rebelled against Johnson over the anti-no-deal Brexit law, said: “It is neither responsible nor acceptable for ‘sources in No 10’ to accuse judges of political bias.

“Criticism of this type from within government undermines the independence of the judiciary and, therefore, the rule of law.”

Theresa May’s former chief of staff, Gavin Barwell added: “This is a very unwise road for a party that believes in a) the Union and b) the rule of law to go down.” 

Scottish Tory MSP Adam Tomkins also had a stark warning for No 10, tweeting: “To politicians who don’t like court judgments: don’t attack the judges or the independence of the legal system.

“Don’t ever do that. Appeal, test your legal arguments in a superior court. Why does this even need saying?” 

Ex-SNP MP Angus Robertson also took to Twitter, saying: “No10 now briefing against Scottish Courts and Scottish judges ‘suggesting they are politically biased’.

“Having been caught out lying to the Queen they are now burning more constitutional conventions.”

After anger at the comments, Johnson’s official spokesman issued this comment: “The prime minister has total confidence in the independence of the judiciary.”

It has also been confirmed that the government will appeal against the ruling at the UK Supreme Court. 

Since the ruling, the PM has come under fresh pressure to reopen parliament after MPs staged a protest in the early hours of Tuesday to stop the prorogation. 

Labour’s Shadow Attorney General Shami Chakrabarti said: “This ruling shows that, despite what Boris Johnson has spent his privileged life thinking, he is not above the law.”