THE UK Government’s opposition to a second independence referendum will become untenable if the SNP win a majority at next year’s Holyrood elections, Professor Sir John Curtice has suggested.

The polling expert said that Boris Johnson cannot “bind” the Scottish electorate, who have the “right to be fickle”.

He also advised Nicola Sturgeon to hint at her plans for a Plan B if Westminster continues to refuse a Section 30 order and warned that internal divisions were the biggest potential obstacle for the SNP.

The Strathclyde University, quoted in the Courier, said: “I’m assuming the SNP will say something much less circumstantial than in 2016 and say, for example, we want a referendum full stop within the next parliament, not if circumstances change.

“So if they make the same promises as in 2011 and they get the same outcome as 2011, the UK Government will be absolutely on the back foot.

“Because the problem with the UK Government’s position is that, yes, sure, you can keep on arguing that the SNP said once in a generation and that they should keep their promises but what you cannot do is bind the electorate.

“And if the electorate decide that they wish to back another referendum and they give the SNP an overall majority, then you cannot say we are going to ignore you. The electorate cannot be bound by the promises that were made by politicians in 2014. The electorate have the right to be fickle, even if your opponents don’t.”

READ MORE: John Curtice: Yes side the favourite to win indyref for the first time ever

Curtice added that the SNP’s Plan A “has to be wanting the UK Government to come up and agree to a referendum” but said the issue could be taken to the UK Supreme Court if the Tories hold firm on their refusal.

He continued: “There is a limit to the extent to which you are going to want to reveal what your plan B is because that potentially takes some of the pressure off the UK Government. That said, I think Sturgeon will need to give some indication that there is a plan B and maybe some indication of what it might mean.

“I think she would be wise, partly just to keep her troops happy, just to indicate what her alternative would be.”

The polling expert also warned that internal splits will pose the biggest risk to the SNP.

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He explained: “The brutal truth, it seems to me, is that the biggest risk the SNP face to the realisation of their ambitions are their own internal divisions.

“Obviously Nicola Sturgeon will face the difficulties of the handling of the Alex Salmond affair and there is a reasonable debate to be had about what are you going to do if you get an overall majority and the UK Government does still say no.

“I suspect Sturgeon will be wise at some point to say a little bit more about that but she’s obviously determined at the moment to say, ‘I’m just not talking about independence at all’.”

READ MORE: Wings Over Scotland party still being considered ahead of election

Two new pro-independence parties – the Alliance for Independence (AFI) and the Independence for Scotland Party (ISP) – have been formed ahead of next year’s election, with Wings Over Scotland not ruling out the prospect of a third.

But the professor said recent survey data suggests alternative options may not be required to secure a pro-Yes majority at Holyrood.

He stated: “At the moment, the opinion polls are saying you’ve never had to worry less about the need to game the system.

“For the moment, at least, the SNP are heading for a whopping great majority, anyway. Things may be different next May but right now one would say it’s just not necessary.

“The obvious risk, then, is then what the Unionist side is going to make of it if there is a significant and serious list vote, particularly with the idea of putting Alex Salmond at the head of the list.”