A veteran SNP MSP has called on Holyrood to hold a second Scottish independence vote even if its fails to win approval of Westminster.
Former health secretary Alex Neil insisted MSPs could press on with a consultative ballot on the issue if the Lord Advocate gave consent to such a move.
But Unionist campaigners branded such a plan as “irresponsible” and claimed Scots deserved better than politicians playing “constitutional games”.
The Prime Minister wrote to Nicola Sturgeon on Tuesday stating that she and her predecessor Alex Salmond had pledged the 2014 referendum would be "once in a generation" event.
But the SNP leader branded the Tories "terrified of Scotland's right to choose" as she warned their opposition will not stand.
Mr Neil told the Daily Record he believes the Scottish Government should seek a legal opinion on whether Holyrood could organise its own consultative referendum without the consent of Westminster.
He said the SNP should consider establishing a Constitutional Convention on the specific issue of Scotland’s “right to choose”.
His remarks come after Constitutional Relations Secretary Mike Russell accused the Prime Minister of ignoring the wishes of Scots voters, who in last month's general election returned an increased number of SNP MPs.
Speaking yesterday Mr Russell said: "I think you can either have democracy or you can have dictatorship, you can't have both.
"If Boris Johnson wants to be a dictator that simply says 'other people's votes don't matter, Scotland's doesn't matter, Scotland isn't a nation', that is a decision which cannot hold in my view, because it goes so much against the views of the people of Scotland.
"Even those who are not in favour of independence, we know are in favour of saying it is right that if the people of Scotland vote for something they get their chance to choose. That is all this is about."
Pamela Nash, chief executive of Scotland in Union, said: “Talking up the prospect of a Catalan-style wildcat referendum is irresponsible.
“The majority of people in Scotland don’t want a divisive second independence referendum, but if there ever is one it must be carried out legally and fairly.
“Trying to break up the UK through the back door is simply not acceptable.
“Scotland deserves better than a government playing constitutional games, and now that a referendum has been ruled out, Nicola Sturgeon should focus on her devolved responsibilities such as schools and hospitals.”