AN SNP MP has insisted the Scottish Government "have in their minds" a route to a legal referendum if Boris Johnson decides not to grant a Section 30 order.

Stewart Hosie, MP for Dundee East, said the "cleanest" way of asking Scots whether they want to leave the UK would be through a temporary transfer of powers from Westminster to Holyrood as happened in 2014.

But he said he felt "confident" the Scottish Government has a plan B and insisted there is a "different route" if the Prime Minister decides "not to be a democrat".

It comes after Nicola Sturgeon and Greens co-leader Patrick Harvie fired the starting gun on a new independence campaign on Tuesday with the release of the first in a series of papers making the case for Scotland outside the UK.

When asked how the Scottish Government intend to get a lawful referendum, Hosie told BBC Scotland's The Nine: "First thing to say is, the Section 30 order, that temporary transfer of powers, is the cleanest and quickest way to do it.

"But I'm extremely confident indeed that if Boris Johnson decides not to be a democrat but to be a despot, then the Scottish Government have in their minds a mechanism to lead us to a legal referendum without a Section 30 order.

READ MORE: Lorraine Kelly calls out Boris Johnson over ITV interview refusal

"There will be a referendum on Scotland's future whether Boris Johnson says yes or whether he says no."

Hosie was then asked when a Section 30 request would be made. 

He replied: "I'm not sure exactly what the timing is in that regard, but clearly they will make the request. 

"I hope at that point the UK Government see sense, and they decide not to carve themselves out of any debate over Scotland's future.

"But if they don't then there is a different route and I'm confident the Scottish Government will take it and the referendum will be held."

Sturgeon said on Tuesday a referendum will be held with or without a Section 30 order. She intends to hold a vote next year.

Scottish Tory leader Douglas Ross said yesterday he would boycott any "wildcat" referendum that is held without consent from Westminster.