NICOLA Sturgeon has thrown down the gauntlet to Boris Johnson and warned he will be “standing in the way” of Scots if he tries to stop Holyrood legislation to hold a second independence referendum.

The National:

Irish Times' journalist Fintan O'Toole in conversation with First Minister Nicola Sturgeon at the newspaper's Winter Nights Festival.

She was discussing the situation with an online audience of Irish Times' readers and it was the first time she had spoken about her government’s alternative route to independence since Constitution Secretary Michael Russell published the 11 point strategy last week.

The plan says if the SNP remains in power after the May election, it will ask the UK Government to either agree a Section 30 order request or to agree to Holyrood legislating to hold an independence vote.

READ MORE: 'Tim'rous beastie': Nicola Sturgeon says Boris Johnson is scared of indyref2

Should Johnson fail to agree to the latter it would be up to him to challenge the legislation at the UK Supreme Court. Earlier this week he refused to say whether he would do so.

Speaking to Irish Times readers - some of whom were watching from as far away as Peru and Kenya, the First Minister said any such court challenge by the Prime Minister to a Scottish Parliament bill to hold indyref2 would not be a position any democratic leader should take.

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She was outlining her government’s so-called Plan B route to independence at the Winter Nights Festival last night, an event run by The Irish Times - which in an editorial earlier this week strongly condemned Johnson's failure to agree a new referendum.

He has repeatedly refused to do so, suggesting earlier this month that there should be a 40 year gap between the two votes.

Columnist Fintan O’Toole asked what would happen if Johnson said no to a new independence referendum even if the SNP won the election in May, having stood on a manifesto to hold a new vote.

READ MORE: Scottish independence: Boris Johnson rules out new vote until 2055

The First Minister replied: “For arguments sake, say he does and he just decide to dig his heels in. Well this question of does the Scottish independence referendum need the consent of Westminster or could the Scottish Parliament legislate itself, that has never been tested in courts and I hope we never get to the point where it would have to be tested in the courts.

“Back in 2014 at the time Alex Salmond and David Cameron decided to put that question beyond doubt and come to an agreement and that’s the precedent we should use if people in Scotland vote for a party that is proposing a referendum, but [if that route is not open] ... we would implement the mandate and if Boris Johnson wanted to say we didn’t have the legal authority then he would have to test that in court.

“He would have to go to court to stand in the way of the democratic wishes of the Scottish people. All I would say to that Boris is ‘good luck.’ It’s not a position any self-respecting democrat ever contemplates finding themselves in.”

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She said she didn’t favour a “Catalonia situation” and insisted any referendum held in Scotland must be legal, constitutional and receive international support.

“I don’t favour a Catalonia situation. Don’t get me wrong, I have huge sympathy for my friends and allies I have in Catalonia who are in a dreadful position, but the referendum in Catalonia self-evidently didn’t lead to independence and I want a referendum that is capable, if people vote for it, of leading to independence,” she said.

“It must be legal, it must be constitutional and capable of attracting international recognition and support. Otherwise it might be a process we all enjoy taking part in but it’s not going to deliver the independence that we want. So it has to be a legal referendum.”

READ MORE: PM refuses to say if he would take Scots to court on indyref2

On the likely prospect of Johnson not consenting to a second referendum even if the SNP win the Holyrood election and form the Scottish Government for a fourth consecutive, she told the festival's audience that it was an "outrageous" position for him to take.

"It's a preposterous, outrageous position to take as what he is effectively saying is that even if I, my party stand in this election on the manifesto commitment offer the people of Scotland a choice of a referendum on independence and people in Scotland vote for that and we have all these opinion polls showing a majority of people want independence he is going to say no.

"What does that say? That the democratic wishes of the Scottish people just count for nothing?

"What then is the democratic route to independence? It's an outrageous, unsustainable, undemocratic and anti democratic position."