A senior SNP MP has suggested the party could withdraw from the House of Commons if Boris Johnson continues to block a second independence referendum.
Perth and North Perthshire MP Pete Wishart said the SNP could consider “withdrawing from the apparatus of the UK state” if Westminster continues to reject calls for indyref2.
This could be “escalated” to the extent of withdrawing the party’s “participation in institutions of the UK Parliament”, he added.
Wishart, who has been an MP for 19 years and chairs the Scottish Affairs Committee, also mooted the possibility of Scotland seeking the support of the EU for an independence vote if the UK Government refuses one.
Johnson and his predecessor Theresa May have repeatedly rejected calls to grant a Section 30 order to allow such a ballot to be held.
They said the 2014 referendum, where Scotland voted to stay in the UK by a margin of 55% to 45%, was “once-in-a-generation”.
The SNP says it has won repeated mandates in multiple elections since 2016 for the right to hold a vote in the event of a “material change of circumstances” – citing Brexit as an example.
Wishart made clear holding a referendum with the UK Government’s agreement, as was the case in 2014, is his preferred approach.
But he said Scotland is now at a “tipping point” – with a poll last month putting support for independence at 54%, and several others giving leads to the independence side.
Western Isles MP Angus MacNeil is among those in the SNP arguing that a majority win in next year’s Scottish Parliament election should be taken as grounds to start negotiations with Westminster for Scotland to leave the UK.
But Wishart argued the party’s manifesto for the next Holyrood campaign must contain a “clear and unambiguous commitment to hold a referendum”, so it is “understood that a vote for the SNP is a vote for a referendum on independence”.
If the SNP wins a majority in 2021 and if the UK Government then continues to reject its calls for a referendum, he said the party should then “be prepared to move beyond the Section 30 process”.
Writing in a blog post, the Perth and North Perthshire MP said: “If the UK refuses to participate in an agreed referendum in the face of majority support and a clear democratic mandate, we must presume that they have decided to exempt themselves from their obligations and responsibilities as a partner in the union.
“We would then have the grounds to seek to secure our independence without their participation.
“This should involve a referendum designed in Scotland where a last invitation is offered to the UK to participate to put the case to remain in the union.
“A request to the EU to sanction this referendum should be made and every attempt to involve them in the designing of that referendum should be pursued.”
He said the Scottish Government should at the same time set out its intention for an independent Scotland to join the EU, saying it should “concurrently start the equivalent of an accession process”.
Wishart added: “Where there is no provision in the EU rules to allow for this we should express our intention to rejoin and seek their approval and participation in designing a process to achieve that outcome.
“We would say to the EU that the UK is refusing our democratic right as a nation to be part of the EU and we should do all we can to keep Scotland aligned with EU regulations.
“Beyond that, we should be looking at withdrawing from the apparatus of the UK state and starting to informally acquire the responsibilities currently exercised by the UK.
“This could start by withdrawing from the inter-governmental infrastructure determining the management of the four nations of the UK.
“This could be escalated up to and including the participation in institutions of the UK Parliament.”
Since the early 20th century, Sinn Fein MPs in Northern Ireland have had an abstentionist policy which means they do not participate at Westminster.
Scottish Conservative shadow constitution secretary Murdo Fraser said: “The fact the SNP is using this time period demand a wildcat referendum exposes the party’s true priority.
“No matter how severe the coronavirus crisis becomes, health-wise or economically, the issue of indyref2 still remains the nationalists’ priority.
“Only a few months ago Pete Wishart thought ‘gentle persuasion’ was the way forward.
“Now we’re in the midst of a global pandemic, he seems to think an illegal, divisive re-run is the preferred route.
“The SNP should be putting all its effort into guiding Scotland through coronavirus and coming out the other side – not selfish constitutional obsessions.”