Prime Minister Boris Johnson’s case that he acted lawfully over the suspension of Parliament for five weeks is under the spotlight at the UK’s highest court.

On the second day of an unprecedented hearing, the Supreme Court in London will hear Mr Johnson’s response to challenges against his controversial move.

During proceedings on Wednesday, his lawyers will urge 11 justices, including the court’s president Lady Hale, to rule in his favour over the legality of his advice to the Queen to prorogue Parliament for a length of time opponents claim was an “abuse of power” and for an “improper purpose”.

The judges are to hear about two and a half hours of submissions from Sir James Eadie QC on Mr Johnson’s behalf.

Sir James will argue that the Supreme Court has no jurisdiction to rule on the lawfulness of the length of prorogation.

He told the court on Tuesday that decisions to prorogue Parliament “are inherently and fundamentally political in nature” and not a matter for the courts.

He said: “They will involve considerations about how most effectively and efficiently to manage the conduct of the Government’s business, including specifically its legislative agenda in Parliament.”

Sir James added that such decisions were “inevitably shot through with assessments of a political kind”.

However, during an exchange with Lord Reed, one of the justices hearing the case, he accepted there are limits to the Government’s prerogative power and that it is part of the court’s role to determine what those limits are and whether they have been exceeded.

(PA Graphics)
(PA Graphics)

He also accepted that prorogation could undermine Parliament’s ability to scrutinise the Government, but he argued: “My submission will be that, despite those features, this is a well-established constitutional function, exercisable and to be exercised by the executive.”

He added: “(The issue is) whether it is appropriate for those controls to be exercised by the courts as opposed to … Parliament. My submission is that these are political judgments.”

The historic appeals arise out of earlier rulings in the English and Scottish courts, in which leading judges reached different conclusions.

At the High Court in London, the Lord Chief Justice Lord Burnett and two other judges rejected a challenge against the Prime Minister’s move by campaigner and businesswoman Gina Miller.

But in Scotland, a cross-party group of MPs and peers won a ruling from the Inner House of the Court of Session that Mr Johnson’s prorogation decision was unlawful because it was “motivated by the improper purpose of stymying Parliament”.

Mrs Miller is now appealing against the decision of the High Court, asking the Supreme Court to find that the judges who heard her judicial review action “erred in law” in the findings they reached.

The justices are also being asked by the Westminster Government to allow an appeal against the decision in Scotland.

Gina Miller
Gina Miller arrives at the Supreme Court (Aaron Chown/PA)

Mr Johnson says the five-week suspension is to allow the Government to set out a new legislative agenda in a Queen’s Speech when MPs return to Parliament on October 14.

But those who brought the legal challenges argue the prorogation is designed to prevent parliamentary scrutiny of the UK’s impending exit from the EU on October 31.

On the first day of the hearing on Tuesday, Mrs Miller’s barrister Lord Pannick QC argued that Mr Johnson’s motive for an “exceptionally long” prorogation was to “silence” Parliament, and that his decision was an “unlawful abuse of power”.

Mrs Miller’s action is supported by former prime minister Sir John Major, shadow attorney general Baroness Chakrabarti and the Scottish and Welsh Governments, who are all interveners in the Supreme Court case.

The justices will continue to hear submissions from the parties and interveners on Thursday, the third and final day of the hearing,  but it is not yet known when they will give a ruling.

Mr Johnson advised the Queen on August 28 to prorogue Parliament for five weeks and it was suspended on September 9.