THE SNP’s failure to win a second Holyrood majority was down to its loss of key constituencies rather than people switching support to the Greens on the list vote.

An analysis published today by the Electoral Reform Society Scotland concludes the 2016 vote was actually more proportional than the “anomaly” of the SNP landslide of 2011.

It also reveals some of the unexpected consequences of the Additional Member System used to elect MSPs, with Scottish LibDem leader Willie Rennie’s win in North East Fife meaning an extra list MSP for the Greens, who then replaced the LibDems as Holyrood’s fourth party.

Jackie Baillie’s victory for Labour in Dumbarton also meant an extra seat going to the Tories.

Despite increasing their constituency MSPs from 53 to 59, the SNP lost 12 of its 16 list MSPs last year, leaving it two short of an absolute majority of 65 at Holyrood.

The report concludes SNP warnings that voting Green on the list would help Unionist parties were largely unfounded, and it was not lists which cost the SNP a majority, but constituency gains for other parties, especially the Tories who picked up four seats.

The report also found the preponderance of male Tories, 25 of the party’s 31 MSPs, meant there was no increase in Holyrood's female representation, which is stalled at 35 per cent.

Author John Curtice, Professor of Politics at the University of Strathclyde, said: “Perhaps the biggest surprise of the Holyrood election was that the SNP failed to secure a second overall majority even though its share of the constituency vote was up on 2011.

“Some of those who voted for the SNP on the constituency ballot do appear to have backed the Greens on the list vote, where the SNP’s tally fell. While this may have cost the SNP one or two list seats, the higher level of support for the Greens helped ensure that there were more pro-independence MSPs at Holyrood than would otherwise have been the case.”

He continued: “The main reason why the SNP lost out was that the party failed to win a number of key constituency contests – in particular, two in Edinburgh and on in Fife, Aberdeenshire and Dumbarton – that the party should have won, given the national swing.

“These failures were not compensated for in the allocation of list seats because elsewhere in the relevant region the SNP had already won its proportionate share of seats in the constituency contests. The result was a more proportionate outcome than would otherwise have been the case – or, indeed, actually occurred in 2011.”

ERS Scotland Director Willie Sullivan added: “As an electoral system, the 2016 Scottish Parliament election showed the Additional Member System in its best light since the parliament was created. AMS did what it was supposed to do, giving the most proportional result yet – perhaps making up for the anomaly of 2011, when the SNP got a majority of seats on around 46 per cent of the vote.”