NICOLA Sturgeon has defended her back-up plan to use a general election as a de facto vote on independence – insisting that a route to dissolving the Union cannot be “completely blocked” by Westminster.

The First Minister has set out her routemap for holding a second vote on independence by pre-empting Supreme Court action against Holyrood holding its own re-run of the 2014 vote.

The Lord Advocate has referred the proposed legislation to the Supreme Court, and if it is found to be competent, the Scottish Government intends to hold a referendum on October 19 next year.

But if the Supreme Court rules that the Scottish Parliament has acted outside its powers with the plans, the First Minister insisted that the next UK general election will be a “de facto referendum” on Scottish independence.

She told MPS that if there is "no lawful way" for a referendum to be held under plans, the SNP will "fight the UK general election on this single question - should Scotland be an independent country".

She added that the next election will be a "de facto referendum" on independence.

Under a de facto referendum, the Scottish Government is likely to focus on the total number of votes cast in the general election rather than seats – to equate it to a Yes/No poll.

If a de facto poll indicates a majority in favour of independence, the Scottish Government would likely begin negotiations with UK ministers over the process for Scotland to become an independent country without a full referendum being held.

Asked by journalists how a general election can be a de facto referendum, Ms Sturgeon said: “I don’t want that to be the route we go down.

“I want a lawful, constitutional referendum – that's what I’m focused on right now.”

Ms Sturgeon added: “If the Supreme Court, and I hope this is not the outcome, say the law means that there’s no legal way for the Scottish Parliament to hold a referendum without the consent of Westminster, Scotland has to have some way of expressing its view.

“If we get into that scenario, I’ll set out much more about exactly what we’re asking people for and what we will do with that.

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“Right now, I have set out a path today that I hope ends in a constitutional, legal referendum.”

The First Minister insisted that “Scotland cannot and will not be in a position where its democracy is a prisoner of Westminster intransigence".

She added: “People will have that opportunity to make their views known on independence and that is what we will put in an election, which is clearly a legal process, we will put that question at the heart of the election campaign.”

Asked repeatedly if Scotland can become independent without a referendum, Ms Sturgeon said: “I want a referendum”.

She added: “Scotland’s opportunity to have its say on independence cannot be completely blocked.

“I want a referendum and that is what I’m focused on.”

Ms Sturgeon labelled a suggestion that her back-up plan to hold a defacto referendum was setting up the country for a unilateral declaration of independence as “ridiculous”.

She added: “I want a constitutional, legal referendum.”