It would be “unimaginable” for a Tory UK government to continue to block another independence referendum after the General Election, according to SNP deputy leader Angus Robertson.
Mr Robertson told the BBC’s Sunday Politics Scotland programme that the position was “unsustainable for unionism”.
The Conservative manifesto says a second vote on independence should not be held unless there is “public consent”, and only after Brexit has “played out”.
The SNP wants a referendum to be held between autumn 2018 and spring 2019, insisting its mandate to demand the ballot was won at last year’s Holyrood election.
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Mr Robertson said: “If the people of Scotland determine that they want SNP representatives at Westminster representing our collective interests, we will all have been sent there to stand up for the rights of the Scottish Parliament, the Scottish Government and the mandate that the Scottish people gave in the last Scottish Parliament election.
“Are we really in a position where the Tories are saying that the people of Scotland will not be able to determine their own future because of what, an opinion poll?
“I just think it is unimaginable, if there is a UK Tory party victory across the rest of the UK but in Scotland the SNP is returned, that they can just continuously turn their backs on the democratically expressed views of the people of this country.”
The SNP’s opponents have accused the party of attempting to play down its bid for another referendum during the General Election campaign.
SNP leader Nicola Sturgeon has focused on telling voters that their support can give her a mandate to influence the Brexit negotiations.
Ms Sturgeon insisted on Saturday that her position on a referendum has not changed, while Mr Robertson told the BBC: “Of course there will be a referendum because the people have determined that we should have a choice about our future.”
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The Conservatives, who have campaigned heavily on their opposition to another constitutional ballot, are hopeful of gains north of the border on June 8.
With the party winning just one of Scotland’s Westminster seats in 2015, the Tories are targeting several of the 56 seats taken by the SNP, including Mr Robertson’s own constituency in Moray.
He dismissed the view that Tory gains could derail his party’s referendum bid.
“The SNP represents most seats in Scotland, not just most, almost every single one, and it’s being suggested now if we were theoretically to lose a seat or two somehow we have lost legitimacy and the mandate we would have been given by the electorate of Scotland somehow does not count - that’s a very, very strange view of democracy,” he said.