Iain Duncan Smith has claimed the Supreme Court “stepped into new territory” with its Article 50 ruling.

The Leave campaigner and former party leader suggested the judges had told Parliament “actually what they should do” after the Government lost its appeal on how Brexit was to be triggered.

But his statement was picked apart by online experts and contradicted by Brexit Secretary David Davis, who told MPs shortly afterwards that the Government “values and believes in” an independent judiciary.

Mr Duncan Smith told BBC2’s Victoria Derbyshire: “There’s the European issue but there’s also the issue about who is supreme – Parliament or a self-appointed court.

“This is the issue here right now, so I was intrigued that it was a split judgment, I’m disappointed they've tried to tell Parliament how to run its business.

“They've stepped into new territory where they've actually told Parliament not just that they should do something but actually what they should do.

“I think that leads further down the road to real constitutional issues about who is supreme in this role.”

The anonymous Secret Barrister, who writes a column for the Solicitors Journal, called the intervention “Trump-like in its audacity“ and “provably false”.

The writer said on Twitter: “There's no issue about who is supreme between Parliament and Supreme Court. It’s Parliament.

“The Court expressly did not tell Parliament how to run its business. It clarified what the [Governmentt] could not do unilaterally.

“The Supreme Court is not self-appointed. It was established by Parliament by section 23 of the Constitutional Reform Act 2005.

“The only ‘real constitutional issues’ are those arising in IDS' own imagination, born of his own unstymied ignorance and base stupidity.”

And Brexit Secretary David Davis told the House of Commons: “We believe in and value the independence of our judiciary, the foundation upon which the rule of law is built.”

The Supreme Court's website sets out how judges are appointed according to the 2005 Act. The Lord Chancellor, a politician, convenes a selection commission which decides who should join the court.