The UK's Supreme Court on Tuesday opened proceedings in a legal challenge to Prime Minister Boris Johnson's suspension of the British Parliament.

Johnson argues that he asked the Queen to prorogue — or suspend — the lower house in order to introduce a new legislative agenda. But critics accuse him of attempting to stymie debate and push through a no-deal Brexit as the UK nears an October 31 deadline.

Last week, Scotland's highest court ruled that Johnson's suspension was an unlawful attempt to silence debate on Brexit in the House of Commons. An English court had earlier ruled that the prime minister's prorogation of parliament was legal.

The Supreme Court will focus on legal arguments and is "not concerned with the wider political issues," Brenda Hale, the chair of the judges, said as she opened Tuesday's session.

Hale added that the legal decision of the court will not determine how Britain leaves the EU.  

Read more: Brexit: Does Boris Johnson's track record explain the man?

Crucial decision

Observers have described the court case as one of the most challenging to reach the Supreme Court in centuries, saying it could have significant consequences.

"If parliament is prorogued with no remedy available then the balance of power is tipped far too heavily to the executive," Sionaidh Doughlas-Scott, law professor at London's Queen Mary University, told Agence France-Presse news agency.

If the court rules against Johnson, it is likely that Parliament would reconvene. However, it is unclear when that would take place.

The court hearings could run through to Thursday with a ruling possible by as early as Friday.

Read more: Brexit: France losing patience with UK uncertainty

Backstop troubles

Meanwhile, Johnson discussed with German Chancellor Angela Merkel renewed efforts to secure an exit deal, according to his spokesman.

"The prime minister reiterated that the UK and the EU have agreed to accelerate efforts to reach a deal without the backstop," the spokesman said. However, the EU has yet to support the omission of the so-called backstop without an appropriate alternative.

The backstop is a regulatory mechanism in the Withdrawal Agreement to ensure that a hard border is not created between the Republic of Ireland, an EU member state, and Northern Island, which forms part of the UK.

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cw,ls/se (Reuters, AFP)