Nicola Sturgeon said that vote, should the Supreme Court state it is not in the power of Holyrood to legislate for an independence referendum, would constitute a referendum.
However, the Scottish Government has refused to clearly define what would constitute victory beyond stating 50 per cent plus one of the popular vote.
Asked whether this number would include the votes of other pro-independence parties such as the Scottish Greens or Alba, the First Minister’s official spokesperson told reporters such a definition would come after the Supreme Court’s judgement.
He said: “Clearly other parties will stand in that election, if we get there because it is still an ‘if’ because we don’t know what the court’s going to say. But if that is a scenario that happens, it will be for other parties to say what they are standing on.
"It is not really for me to talk about, strictly speaking, SNP party issues around this table.
"But it is certainly not for me to speak about what the Scottish Greens or any other party might put in their manifesto.”
Pressed on the fact it is ultimately for the Scottish Government to define and the fact the Greens are part of that government, Ms Sturgeon’s spokesperson added: “Indeed, but we’re not there yet.
"Let’s wait and see what the Supreme Court say and if and when we end up in a scenario where we are talking about this stuff, we can have these conversations then.
"But it is not for us to speak on behalf of other political parties.”
In 2015 – the SNP’s strongest result in a general election – the party received 49.97 per cent of the popular vote.
With the Scottish Greens, who received 1 per cent, the ‘de-facto referendum’ could have been won.
Without Green votes, it would have been considered a defeat.
A spokesperson for the Scottish Greens said: “Our preference is for a referendum to take place.
"Should the court rule that one cannot take place, then the next opportunity for the people of Scotland to demonstrate their democratic will would be at a general election.
"Our strategy for such an election will be, as always, a matter for discussion within the party.”
The debate comes as SNP Commons leader Pete Wishart said the UK Government was trying to “imprison” Scotland in the Union.
Mr Wishart asked the Government to organise a debate about democracy in the UK, amid claims it had been put in “some sort of Tory deep freeze” where people cannot change their minds.
But Commons leader Mark Spencer described Mr Wishart as the “master of smoke and mirrors”, adding the SNP MP did not want to focus on other matters such as the “disastrous” education system in Scotland.
Speaking at business questions, Mr Wishart said: “We need to properly consider why this Government thinks it’s OK to try and legally imprison a nation in what is supposed to be a voluntary union of equals.
“We need to figure out why this Government seems to believe that somehow democracy can be put in some sort of Tory deep freeze where people aren’t allowed to change their minds."