ALBA has called for a Scottish Constitution Convention to be established following the Supreme Court's ruling on Indyref2.

The pro-independence party, led by former first minister and SNP leader Alex Salmond, has appealed for the move as the court hears a case next week on whether Holyrood has the legal power to hold an independence referendum without agreement from the Westminster government.

Judges are expected to give their assessment in the coming months, though most experts believe that with the constitution a reserved matter they will rule against the Scottish Government.

The matter was referred to the court by the Lord Advocate after the Prime Minister and her predecessor said they would not consent to transfer powers to Holyrood under a Section 30 order to ensure a legally watertight vote.

First Minister Nicola Sturgeon will use the next general election in 2024 as a "de facto" referendum on independence should the judges rule against Holyrood's having the legal powers to hold the vote.

However, Alba depute leader Kenny MacAskill, a former SNP cabinet minister, cautioned against the proxy referendum plan and called for a new constitutional convention, modelling one created in the late 1980s which preceded the re-establishment of the Scottish Parliament.

“It has always been the case that it was for the Scottish Government to set out both the timetable and the means by which it would deliver an independence referendum by the end of 2023 with or without a Section 30 Order being granted by Westminster," he said.

“However the issue of Scotland’s right to choose will be put to the test next week. If as widely expected the Supreme Court rules that Scotland’s Parliament does not have the legal right to hold an independence referendum the futility of referring the matter to the Supreme Court, in the first place, will have been exposed for all to see. "

He added: “The key question then will be 'who decides Scotland’s future?' Is it the people of Scotland through their elected representatives or a Prime Minister and Government at Westminster who our people have never elected?

“In the wake of the expected defeat in the Supreme Court we must take immediate and decisive action to shift the focus of the debate back to Scotland, where it belongs, rather than waiting for the next UK Election, which could be as late as Autumn 2024.

“That is why Alba is proposing a Scottish Constitutional Convention comprised of MSPs, MPs, council leaders, trade unions, civic Scotland and the wider community. Such a convention can play a vital role in asserting the democratic right of the people of Scotland to decide their own future, it would help secure the united political and civic independence movement, a prerequisite for success in any future referendum, and it will signal to Westminster and the international community that Scotland is on the march once again.

“No legal judgement from the Supreme Court or act of the Westminster parliament can override the sovereign will of the Scottish people to determine our own constitutional future. This is the time for our government and our parliament to assert that sovereign will.

“The ruling of the Supreme Court will be a defining moment for Scottish Democracy. This Conservative Government’s difficulties can yet become Scotland’s opportunity but only if we seize the initiative and stop handing the Tories a veto over our future. That is why we must take the urgent action necessary and establish a convention without delay.”

The SNP were approached for comment.