SNP policy is to legislate in Holyrood for another vote if the UK Government rejects requests to devolve the necessary powers needed to hold one.
Such legislation would inevitably be approved by Holyrood given the majority of pro-independence MSPs, but it would then be challenged by Westminster in court.
The UK Government and unionists north of the border have been loathe to say whether they would take the matter that far, but a plan laid out by the SNP earlier this year said it would “vigorously” oppose such a challenge.
Former civil servant Professor Ciaran Martin, who was constitution director at the Cabinet Office between 2011 and 2014 and even sat alongside then prime minister David Cameron during the signing of the Edinburgh Agreement in 2012 – which granted the powers for the 2014 referendum – has said he does not think the Scottish Government would win any such court case.
Speaking at the Edinburgh Book Festival on Wednesday, Prof Martin said: “Holyrood will begin to legislate for a referendum anyway, probably at some point next year, and it will likely end up in court.
“I think, but I’m not a lawyer nor can anyone predict court cases with confidence, but I think the Scottish Government will lose.”
Prof Martin said even if a referendum was granted in court, there could be other obstacles put in the way of another vote.
“Ultimately, I think that even if they pull off a surprise win, Westminster could change the law, they could refuse to recognise the result or unionists could boycott the vote,” he said.
“My point here is that in law the smooth path to independence sought by Scottish nationalists depends entirely on Westminster’s acquiescence, so if Westminster withholds that acquiescence then there’s a stalemate.
“We’re heading for a stalemate and how a stalemate plays out is something I can’t predict.”
Prof Martin, who now teaches at Oxford University’s Blavatnik School of Government, also looked at recent polling on independence, which has shown a drop in support from its peak last year.
One poll for STV News previously put support for independence as high as 58 per cent, but studies done since the turn of the year have shown a slide in support.
“The union in 2021 is in better shape than in 2020, but apart from that the prospects for it are in worst shape than any time, I would venture, since the 1760s,” he said.
“It’s not even, in my view, better than it was on the morning of September 19, 2014 [the day after the first referendum].”
The former civil servant said the 45 per cent vote in favour of independence in 2014 was an “astonishing figure”, adding: “That seems to have established a floor, not a ceiling in terms of support for independence.”
The Alba party, which was led by Alex Salmond at May’s Holyrood election, had claimed earlier this month that Scottish independence was not being pursued with “democratic determination”.