At a meeting of the party’s national council on Sunday, the Greens said if there was no second referendum in October 2023 on the future of Scotland’s place in the UK, it would fight the election on the constitutional question.
Patrick Harvie and Lorna Slater, the Scottish Greens’ co-leaders, said in a statement: “The people of Scotland have repeatedly returned pro-independence majorities to Holyrood and Westminster.
“They must have their say.”
First Minister Nicola Sturgeon said last month that she intends to hold another independence referendum on October 19 2023, but only if the Supreme Court ruled it was legal.
The policy brings the Scottish Greens in line with the SNP, who have also said the next general election would be fought on the single issue if an independence vote is shot down.
“Scottish nationalists accepted that their referendum was a once-in-a-generation opportunity, and I will hold them to that,” she said.
Mr Harvie and Ms Slater, whose party aims to stand a candidate in every constituency for the first time, said: “Our preference is still for a referendum to take place in October 2023.
“Should that prove impossible, then we will contest the next UK general election as a de-facto referendum.
“In that circumstance we want to put the unique Green case for independence to every voter in Scotland.
“And every vote cast on that basis will count as a vote for Scotland to become a Green and independent country.”
But Pamela Nash, chief executive of pro-UK group Scotland in Union, said there was “no such thing as a de facto referendum”.
“People vote for parties in an election on a whole range of issues, and the next election will be about the economy, the climate emergency and many other topics,” she said.
“Just like Nicola Sturgeon, the Greens are acting against the will of the people of Scotland.
“Poll after poll shows that the vast majority of us do not want a second referendum, and want the government to focus on what really matters.
“Rather than divide the people of Scotland, as part of the UK we can invest more in public services, work together to tackle the climate emergency, and unite our people and communities.”