Boris Johnson and Scottish Secretary Alister Jack have been accused of "abandoning" an agreement made between all political parties after the result of the 2014 independence referendum.
The position of the UK government not to grant a Section 30 Order to the Scottish Government to hold a second referendum, goes against the Smith Commission report, according to an SNP MSP.
The Smith Commission met in the aftermath of the 2014 vote to thrash out new powers for the Scottish Parliament, which were later set out in the Scotland Act 2016. However, the cross-party agreement also stated that “nothing in this report prevents Scotland becoming an independent country in the future should the people of Scotland so choose.”
Now Linda Fabiani has written to Alister Jack after his announcement yesterday that there would be no indyref2 even if the SNP is returned with a majority at next year's Holyrood elections - demanding the UK government recommit to the Smith Commission agreement.
Ms Fabiani, who was an SNP representative on the Commission, said: “A key principle, agreed by all five parties on the Smith Commission, is that people in Scotland have the democratic right to choose independence.
“This commitment is in black-and-white in the document agreed by your party and your government.
“Comments by yourself, and by other representatives of the UK government, suggest that you have now abandoned this key tenet of the Smith Commission.
“This would be a gross betrayal of the promises made to the Scottish people both during and after the 2014 independence referendum. I would be grateful if you could now confirm whether the UK government continues to respect and uphold the Smith Commission."
The SNP has stepped up its demands for a second independence vote in light of the December general election which saw it return 47 MPs to Westminster, while the Scottish Conservatives had their MP numbers reduced to six.
Yesterday Mr Jack said the outcome of the 2014 referendum, in which 55 per cent of voters, voted to stay in the UK, had to be respected. He said: "It's about once in a generation and once in a lifetime, that's what people voted for."
Mr Jack added that support for pro-union parties versus pro-independence parties had not actually changed since 2014 when only 45 per cent voted to leave. "A referendum is about a straight result, it's not about first past the post system," he said.
"I still equate it to the number of people voting for Unionist parties and I don't think that that number has changed over the last five years."