10:26

It was a striking figure, perfectly timed for Nicola Sturgeon’s eve of conference disclosure on Sunday she would support a second Brexit vote. According to a YouGov poll for the People’s Vote campaign released that day, 79% of Scottish National party members backed that stance. YouGov also found that 81% would favour a public vote if the UK government proposes leaving the single market.

But political scientists are sceptical about the poll’s results. And while it is unscientific, only a handful of SNP conference delegates backed the people’s vote at a Brexit fringe meeting on Sunday.

Professor James Mitchell, of Edinburgh University and co-author of the largest independent studies of SNP members, said he doubted it was truly representative of the SNP’s membership.

YouGov had a sample 665 SNP members drawn from its large panel of poll participants. Only 11% of those said they voted leave in the 2016 EU referendum, and 478 or 73% of its sample were aged 50 over – and of those, 201 were over 65. And 43% were female.

So this was a largely male and elderly group of pro-EU political activists. There was no weighting against the SNP’s actual membership and no information on where they lived, their educational background or social class.

Mitchell’s survey of SNP members has a quite different profile: the median age of SNP members is 56, with 50% aged under 54. By contrast, the YouGov poll has more women than the SNP as a whole: Mitchell found 38% were female overall.

And is the SNP as Europhile as YouGov suggests? A Survation poll for the Sunday Post this weekend confirmed a long-standing finding that about a third of SNP supporters voted to leave the EU in 2016: far more than in YouGov’s sample.

Seeing the YouGov data, Mitchell said:

Having surveyed [SNP members] after the surge and again we surveyed the most recent surge personally, I have my doubts about this survey. It involves self-selection – only those who have chosen to be part of Yougov sample and we can safely assume are more active. This is probably a reasonable account of SNP activists but I would expect the wider membership might not have these views.

YouGov defended its methodology, arguing it is standard practice in researching “niche groups” to offer unweighted data and party members tend, by definition, to have very similar views to each other. They also said that uniformity was underlined by every age bracket in their poll showing very similar views on Brexit.