THE SNP's Joanna Cherry QC will today mount a legal challenge to the Prime Minister’s threats to defy the law and refuse to seek an extension to avoid a No-Deal Brexit in 27 days.

The action, which is being led by businessman Vince Dale along with Jolyon Maugham QC, will ask Scotland’s highest civil court to mandate Boris Johnson to seek an extension to avoid crashing out of the EU without a deal.

Under the cross-party Benn Act, the UK Government must ask for a further extension to Article 50 to the end of January from the EU by October 19, unless the House of Commons has approved a concluded deal with the EU or expressly voted for a No-Deal exit.

The Prime Minister has repeatedly said that no matter what the circumstances the UK will leave the EU on October 31 and has said he would “rather be dead in a ditch” than request an extension.

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“We are less than 30 days away from the Brexit deadline and the rhetoric and actions of Boris Johnson carry all the hallmarks of a government pushing ahead towards a catastrophic No-Deal Brexit – which we know will hit the economy, cost thousands of jobs and harm people’s livelihoods,” said Cherry, who is a QC as well as the SNP’s spokeswoman on justice and home affairs at Westminster.

“Like much of what Boris Johnson says there is a gulf of truth between the obvious facts of the matter and what he and his government have been saying.

“He cannot be trusted, and this court action is about ensuring he abides by the law. If Boris Johnson tries to defy the law and defy both the Holyrood and Westminster Parliaments by crashing out of the EU without a deal – then we are calling on the Scottish Courts to uphold the law.”

Cherry’s new legal battle follows her success in spearheading a challenge over the prorogation of Parliament last month.

The Court of Session found that the Prime Minister had unlawfully shut down parliament with the decision upheld last week by the Supreme Court in London.

She added: “Last week, the UK Supreme Court unanimously ruled that Johnson’s attempt to shut down Parliament was unlawful, void and of no effect. He must be reminded that he is not above the law.”

Maugham QC added: “This is a very simple case. Our Supreme Parliament – elected from 46 million – has directed the Prime Minister – elected from 160,000 – to seek an extension. That is the law, and no man or woman is above it.”

Action in the Outer House of the Court of Session in Edinburgh today is the first stage in forcing Johnson to abide by the law. The case will proceed to the Inner House on Tuesday where the petitioners will request the court use its unique power of nobile officium and empower a court official to sign the extension letter if Johnson refuses to do so.

The Supreme Court ruled that Johnson’s advice to the Queen that parliament should be prorogued for five weeks at the height of the Brexit crisis was unlawful.

The unanimous judgment from 11 justices on the UK’s highest court followed an emergency three-day hearing the previous week that exposed fundamental legal differences over-interpreting the UK’s unwritten constitution. It led to calls for Johnson to resign as Prime Minister which he rejected claiming he “strongly disagreed” with the court ruling.