By Kathleen Nutt

Political Correspondent

LIZ Truss cannot stop Nicola Sturgeon treating the next general election as a referendum on independence, according to the UK's top pollster.

Sir John Curtice, professor of politics at the University of Strathclyde, said Conservative ministers may try to block indyref2 from taking place next year should a ruling in the Supreme Court on the legality of a vote without the UK's government consent go in the First Minister's favour.

However, he added that UK ministers could not prevent how voters regard the following year's Westminster election which the First Minister wants to treat as a "de facto" referendum on independence.

Sir John's view appears to contrast with that of James Mitchell, professor of politics at the University of Edinburgh, who criticised Ms Sturgeon plan.

The Scottish Government intend to hold a second independence referendum without the consent of UK ministers using Holyrood powers, but amid uncertainty over whether the parliament has the legal authority to do so, the Lord Advocate has referred the matter to the Supreme Court.

Should judges decide that Holyrood can unilaterally stage the vote the First Minister proposes it would take place on 19 October next year.

If they decide that the parliament has not got the powers Ms Sturgeon has said she would not push ahead with the 2023 vote and instead use the general election as a "de facto" referendum regarding the pro-independence side to have won if they succeed in winning more than 50 per cent of votes.

Speaking to The Herald on Sunday last week ahead of the eighth anniversary of the 2014 referendum today, Sir John said: "If it wants to this [UK] government can stop the referendum, what it cannot do is to stop the next general election being a referendum on the constitution because that is a question for voters to decide and for the most part that is already what voters are doing in Scotland.

"The 2021 Scottish Parliament elections was pretty much a referendum on independence. There are some things the UK Government can control but in the end they cannot control voters."

Sir John added if the UK Government did try and stop an independence referendum in 2023, which had been approved by the court, it would likely increase support for the SNP. He said UK ministers may find a way to change the rules on what conditions could precipitate a referendum.

Sir John referred to a report in the Sunday Times earlier this month that the UK government were mulling over the possibility of bringing in legislation to require more than half of Scotland’s entire electorate, rather than a simple majority, to vote to leave the Union for the result to be valid.

A further condition reported to be under consideration may be that evidence would be required for more than a year that at least 60 per cent of voters want a new referendum on independence before the UK government would consider the matter.

Alister Jack, Secretary of State for Scotland, appeared to row back on the reported plans telling BBC Scotland’s there was no need to bring forward legislation as there would not be a vote.

“We don’t see any need to make any adjustments around the rules of referenda at all because, as I say, we’re focused on delivering for people, not having constitutional upheaval through a referendum campaign,” he said.

An amendment by Labour MP George Cunningham to the 1979 devolution referendum legislation required at least 40 per cent of the total electorate to back the proposition. While Yes won 52 per cent of those who voted, this figure was only 32 per cent of the electorate, meaning devolution did not go ahead then.

The rule did not apply in the 1997 devolution referendum with 74 per cent of voters supporting devolution including 63 per cent who said the Scottish Parliament should have tax raising powers.

As part of the Good Friday Agreement, an explicit provision for holding a Northern Ireland border poll was made in UK law. The Northern Ireland Act 1998 states that “if at any time it appears likely to him that a majority of those voting would express a wish that Northern Ireland should cease to be part of the United Kingdom and form part of a united Ireland”, the Secretary of State shall make an Order in Council enabling a border poll.

It is not clear exactly what would satisfy this requirement, for instance whether it would mean a consistent majority in opinion polls, a Catholic majority in a census, a nationalist majority in the Northern Ireland Assembly, or a vote by a majority in the Assembly. However, the Secretary of State must ultimately decide whether the condition has been met.

Last year Mr Jack was accused of rewriting the Good Friday Agreement when he said that Whitehall would grant another independence referendum if polls consistently showed 60 per cent of voters supported one.

“The trigger in my mind, and I look to the situation in Northern Ireland for instance, if 60 per cent of people wanted a referendum and that position was sustained for over 12 months, then I can see there would be a desire for a referendum,” he told STV in October.

Social Democratic and Labour Party (SDLP) leader Colum Eastwood MP said Mr Jack’s comments suggested a “slim understanding” of both the needs of Scotland and the constitutional settlement in Ireland.

It is not clear that if a new referenda law was introduced it would apply to just Scotland or whether it would also apply to Northern Ireland.

Sir John said it was uncertain which side would win a referendum if it did take place in Scotland next year with neither side currently having political momentum.

He added that the critical arguments would come down to the economy, the strengths of the Scottish Government's indyref2 prospectuses on border, trade and currency, and how people viewed the alternatives of Scotland in the UK or Scotland in the EU.

"We've not really had a debate about the choices Scotland will now face which is a very different choice from 2014," he said.

"It will also have to look at what is in Scotland's long term geopolitical interests. Is it in Scotland's interest still to be allied with a country that is a member of the G7, one in the UN Security Council or is it more useful to be allied with the European Union, which is becoming more strategically important and contains Europe's biggest power Germany.

"It is asking people to make decisions about long term strategic choices but we've not had this debate and until we've had we don't know how public opinion will go."

He added: "We may not be choosing between two alternative versions of milk and honey it may be a question of which option do you think will be least bad."

Meanwhile, Sir Tom Devine, who voted for independence in 2014, told The Herald on Sunday he believed the priority now for Scots was not the constitution but voting out the Conservative Government.

Sir Tom said: "Much more important at the moment than a referendum, which I don't think many even loyal independence supporters is a good idea at the moment, is to get rid of this [UK] government. And not only that, it's to ensure that that party will never get into power again for at least two further general elections. They have to be sent away to use the Scottish phase 'to think again'."

He said if there was another independence referendum Scotland faced major difficulties which didn't exist eight ago.

"Supposing there is a Yes vote at some point in the future, there are two major impediments [to independence]. The first is that there would be a period of time before there is re-entry into Europe and at the same time we would no longer be part of the UK common market.

"In other words Scotland would be in the cold for an extended period of time and remember 60 per cent of our exports go south."

The Herald pointed out that there would be a transition period with the UK to keep Scotland trading freely with the UK while waiting to join the EU.

Sir Tom said: "I don't believe if it involved the current Conservative government that negotiations would be in any way amicable."

"But the second issue which makes the first point academic is that there is absolutely no possibility in my view of the current government acceding to another referendum," he said.

He added that he believed the reason why former Prime Minister David Cameron agreed to a referendum was that he was "absolutely certain of demolishing the SNP" and at the time less than a third of Scottish voters were in favour of independence compared to the current situation with the population roughly split 50-50.

Sir Tom said: "And look what happened. There's no a chance whatsoever that the UK Government will surrender to this. Once bitten twice shy."

He reflected on voting Yes in 2014 saying he did so as his first choice of maximum devolution wasn't on the ballot paper.

Sir Tom said: "It was a pragmatic decision as my first choice devolution maximus was not on the ballot paper.

"I just thought, the circumstances, the autonomy of Scotland, the fact there was a new Scottish Government with a lot of dynamism made it attractive.

"Whether I would do the same now, is quite a different issue."

In June Professor Mitchell insisted: “There’s no such thing as a de facto referendum.

“An election is simply not a referendum, a de-facto referendum or any other kind of referendum.”

He questioned plans to use the next Westminster vote in this way insisting it is “not for a political party to dictate the terms of an election”.

Speaking to ITV Border’s Representing Border programme, the academic said: “There are elections and referendums and they are quite distinct.

“In an election the vote is allowed to choose what he or she wishes to choose to determine their vote. It doesn’t have to be about one issue, it is rarely about one issue, but about a range of issues.

“It is not for a political party to dictate the terms of an election.

“In a referendum the question is very clear, that is the whole point of a referendum, it is focused. There isn’t the same focus in an election.”