A POLL commissioned by a Unionist group has backfired, with expert John Curtice saying it highlights growing support for independence and a swing in favour of holding a second vote "sooner rather than later".

The Strathclyde University politics professor also says research points to support for a referendum growing at virtually the same pace among both Yes and No voters.

Writing in his blog, What Scotland Thinks, on the anniversary of the 2014 vote, Curtice says it appears to becoming more difficult to sustain is the argument that Scotland does not want a second referendum "anytime soon".

A Survation poll for Scotland in Union, released late on Tuesday night, put support for a second vote at 42%. Six months ago, the figure was 31%, according to Curtice. 

The Scotland in Union poll also showed that only 28% of Scots think there should never be another referendum. When Scotland in Union asked a similar question in April, the figure was 34%.

Curtice writes: "We first noted during the summer that there were indications that support for Yes had increased somewhat, and had done so primarily as a result of a swing, in particular, among those who had voted Remain.

"It seemed there was prima facie evidence that disenchantment at the prospect of Brexit had now persuaded some Europhile voters to switch in favour of Scottish independence. Since the initial blog in which we identified these trends, they have been replicated by two further polls, one by Lord Ashcroft and one by YouGov. 

"The latter found that, after leaving aside those who said Don’t Know, as many as 49% said they would vote Yes, the same as in April. Meanwhile, 57% of those who voted Remain in 2016 said that they would vote Yes, up 10 points on the figure in June of last year."

Curtice adds: "There is a consistent pattern across all six poll readings of independence vote intentions published so far this year. 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."

Curtics says the polls also show an increase in support for independence among voters who want to remain in the EU, adding: "The claim that Brexit does not pose any risk to Scotland’s future membership of the Union now looks significantly more difficult to sustain."

He goes on: "Indeed, also seemingly becoming more difficult to sustain is the argument that Scotland does not want a second independence referendum anytime soon.  

"A swing in favour of holding another referendum sooner rather than later is also recorded in a poll undertaken by Survation and published today by the Scotland in Union campaign.

"When, six months ago, voters were presented with a range of options for the timing of another ballot, just 31% opted for holding one within the next five years. Presented with a similar set of options now, 42% express that view.

"This apparent increase in support for another ballot is not simply a consequence of the swing in favour of independence itself. True, those who voted Yes are consistently much more likely to back an early ballot than are those who voted No.

"However, both Panelbase and YouGov suggest that the swing since last year has occurred at more or less the same pace among those who voted No as it has among those who voted Yes.

"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?"