UNIONISTS are becoming “increasingly desperate” as support for a second referendum grows, the SNP have said.

Depute leader Keith Brown said there were moves to put fresh barriers in the way of another poll on the country’s future, with “panic” among No campaigners.

His comments come after leading polling expert Professor Sir John Curtice said support for Yes is growing and the argument that Scotland does not want indyref2 anytime soon is becoming “more difficult to sustain”.

However, interim Scottish Tory leader Jackson Carlaw said last week the SNP would not have a mandate for a referendum unless if they “can’t get more people to vote for them than voted against independence.”

Assuming the same turnout as in 2016, this would require the SNP winning 87.83% of the vote at the next Holyrood election, the party said.

Last week Scotland in Union also published an independence poll with the question asked in new wording – of a Brexit-style Leave/Remain.

The survey put the no vote at 59%, however Curtice pointed out it shows a swing in favour of holding another referendum sooner rather than later.

And the Scotland Matters group, which includes figures from the Better Together campaign of 2014, lodged a parliamentary petition calling for any constitutional change to be backed by two-thirds of voters.

That would mean a 65% vote in favour of independence would still result in a loss for the Yes side.

First Minister Nicola Sturgeon says she aims to hold a second referendum late next year, but the UK Government has said it will block a request for the power to hold the poll.

Brown said: “The facts are simple: the SNP has a mandate for a referendum, the Scottish Parliament has voted for a referendum and the Scottish people want an independence referendum.

“With support for independence growing, the Tories are holding democracy in contempt by opposing a fresh vote.

“Jackson Carlaw has clearly been learning lessons from Boris Johnson.

“No campaigners are so panicked they’re inventing all sorts of fresh barriers to put in the way of voters getting a say – wanting to rig the question and refuse a referendum until 9 out of 10 Scots are voting SNP.”

He added: “This is increasingly desperate – and is hardly the approach of people confident in the strength of their arguments.

“No wonder more and more Scots believe Scotland’s future is best served as an independent country.”

In a blog marking five years since the first independence referendum, which was published last week, Curtice said there is a consistent pattern across six polls published so far this year.

He wrote: “On average, they put support for Yes (after leaving aside Don’t Knows) at 49%, four points up on the figure of 45% in polls conducted in the second half of last year.

“As a result, nobody can be sure what the result would be if an independence referendum were held now.

He also pointed out all the increase in support for Yes has occurred in those who voted Remain in Brexit.

He wrote: “The claim that Brexit does not pose any risk to Scotland’s future membership of the Union now looks significantly more difficult to sustain.”

Curtice said two polls that have asked the same question about when a referendum should be held suggest the country is now evenly decided on the subject.

But he said an apparent increase in support for another ballot was not just among those who voted Yes.

He added: “Is there, perhaps, a slowly growing feeling on both sides of the constitutional debate that maybe another attempt will have to be made to resolve the issue before too long?”