NICOLA Sturgeon’s plan to fight the next general election as a ‘de facto’ referendum on independence is a “last ditch” move, her Green allies in government have said.

Minister Patrick Harvie also said that if the UK government ignored a pro-independence majority in the election, “then the UK is no longer a democracy”. 

The First Minister confirmed the plan in November after the UK Supreme Court ruled that Holyrood lacked the power to stage Indyref2 without Westminster’s consent.

With the UK Government refusing to grant temporary referendum powers to Edinburgh, the First Minister said the next election would be fought solely on independence instead.

However there is unease among SNP figures as to how this would work in practice, and the Unionist parties have rejected the idea and say they will fight the election on traditional lines.

Even if the pro-independence parties gained more than 50 per cent of the vote in Scotland, the next Prime Minister could refuse to recognise it as a mandate for ending the Union.

Other countries could also be reluctant to recognise an unconventional process, especially as Ms Sturgeon has previously insisted a legal referendum was vital.

In an interview with the Scotland on Sunday newspaper, Mr Harvie and his fellow Scottish Green co-leader and minister Lorna Slater, discussed the issue.

Mr Harvie rejected outright the suggestion that a pro-independence majority vote in the election should be read as a mandate to hold a legal independence referendum.

He said it would be a mandate for independence itself, not another vote.

He told the paper: “If we are left with a de-facto referendum as the only option, that is in place of the referendum that we ought to have, that we deserve to have, that we have a right to have, it’s not about triggering another one, it’s about answering the question.”

He said the will of the people of Scotland “needs to be asserted democratically" and that a referendum of the kind run in 2014 was the “preferred way of doing that”.

However, “if an election is the only way of doing that, then that’s the last ditch”.

He said: "If that’s the only option they leave us and we take through that process and they ignore the result, then the UK is no longer a democracy."

Ms Slater accused the Unionist parties of “cowardice”, blocking a vote to avoid defeat.

She said: “They have to provide that framework [for a democratic route to independence] for us, that is in their court. 

“To me it’s not a point of principle if they are not doing it, it’s a matter of cowardice.”

"They don’t want to talk about the Union. They know we have a better story to tell and so they do the only thing they can, which is block the referendum.

"They should have the courage of their convictions. If they think the Union is so great, they should come up and debate with us on it.”

The SNP is to hold a special one-day conference in Edinburgh in March to thrash out the details of the ‘de facto’ plan.

The party’s new leader at Westminster, Stephen Flynn, has hinted he is not wedded to Ms Sturgeon’s idea, which would complicate the election for him and other MPs.