AN increasingly “conservative” Supreme Court could scupper the Scottish Government’s plans to hold a second referendum, an expert has warned as a renewed debate over the constitutional question broke out over the weekend.

SNP chiefs are said to be considering a “consultative” referendum in the hopes this will be easier to get past legal challenges, according to reports.

The battle to hold a second, legally-binding vote will be fraught, warned constitutional expert Aileen McHarg.

McHarg, professor of public law and human rights at Durham University, has previously called the case for the Scottish Government holding a vote without Westminster’s permission “arguable”.

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But in an interview with Scotland on Sunday, she warned the Supreme Court had “become quite conservative” on constitutional matters since she first made the argument in 2012.

She said: “When I first wrote on this back in 2012, I thought that the case was arguable that they might uphold the validity of a bill.

"I didn't think it was by any means certain, but I thought it was arguable.

"Since then we've had quite a lot more jurisprudence, a lot more case law from the Supreme Court on devolution.

"We're also in a period where the Supreme Court has become quite conservative in its constitutional jurisprudence.”

A fundamental tripping point for the Yes side, she claimed, was that “the UK Parliament has to agree to dissolve the union”.

Sounding a more encouraging note for independence supporters, she added: “That doesn't mean that a unilateral process is completely pointless. It can serve a political purpose, it can continue to put pressure."

Ciaran Martin, an ex-cyber spy and former constitution director at the UK Government, argued in The Sunday Times that the Scottish Government could change the wording of the next referendum to simply ask voters whether they thought indyref2 negotiations with the London Government should begin.

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Martin said this may “stand a better chance in court” than a referendum asking whether Scotland should become an independent country.

He wrote: “The talk in Edinburgh circles is of a clever legal wheeze where softer legislation is drafted.

"Perhaps instead of a referendum on independence, the bill is instead about something like asking the people of Scotland for a mandate to open independence negotiations with the UK.

"Something like this might stand a better chance in court, though experts are sceptical.”

Reports in Saturday’s Times suggested SNP high command looked favourably on a consultative referendum paving the way for a second, legally-binding vote on Scotland’s future.

Prime Minister Boris Johnson has said he will refuse a Section 30 order for a second referendum, claiming the 2014 vote settled the independence question.

His ministers have told the Scottish people they must wait until 2039 before the question could be re-run.

Constitution Secretary Angus Robertson has said the Scottish Government plans to hold indyref2 in October 2023 and the First Minister has said this will go ahead with or without a Section 30 order.