Prime Minister Andy Burnham is being challenged to "bring it on" and allow a second independence referendum, with a senior member of John Swinney's Government insisting the Prime Minister should "let the people of Scotland decide".
Stephen Flynn, the Economy, Tourism and Transport Secretary, is expected to call on Mr Burnham to offer a "constitutional choice" to Scotland's voters when he opens the SNP conference in Aberdeen on Thursday.
Demand for a constitutional choice
Mr Flynn, the former SNP Westminster leader who moved to Holyrood after May's Scottish election, will issue the demand as the party's conference gets underway. Scotland's First Minister John Swinney is pushing for another referendum to be held before 2031 and has already declared he believes Mr Burnham, who is expected to visit Scotland on Friday, will be the last prime minister of the United Kingdom.
The Labour leader, however, used his own conference speech recently to declare he is "utterly determined" that will not be the case. He was forced to row back from comments made earlier this year, when he appeared to suggest another referendum could take place under certain circumstances.
SNP's pro-independence campaign
With the SNP planning what it says will be the biggest pro-independence campaign since 2014, Mr Flynn will use his conference speech to issue a challenge to the Prime Minister on the constitution. He will say: "Our message to Andy Burnham is simple. If he believes the United Kingdom status quo is worth saving – then bring it on, and let the people of Scotland decide."
Mr Flynn will add that any debate on Scotland's future will be a "constitutional choice will between the ambition of the Scottish National Party versus a narrow Westminster vision". While the SNP supports a "new Scotland in the European Union", he will claim the Westminster parties favour an "old idea of what the United Kingdom once was".
Mr Flynn will tell SNP supporters: "We are the party of independence. We have a vision for Scotland. Not rooted in memories of a country that was, but of what a country can be." He will also claim that Mr Burnham's future in Downing Street is linked to him being able to keep the UK intact.
Political context and reaction
Sir Keir Starmer stepped down as prime minister in the wake of poor election results for Labour in May. The SNP saw off a challenge from Scottish Labour to win their fifth consecutive Holyrood election while, in Wales, Plaid Cymru became the largest party in the Senedd, ousting Labour from power there.
Mr Flynn will speak about how the "electoral success" of nationalist parties has "far reaching consequences right across these islands". He will add there is "no doubt that the electoral success of our friends in Plaid in Wales, and of ourselves here in Scotland, ended the reign of yet another Westminster prime minister".
The SNP MSP will say Sir Keir was the "eighth prime minister to tumble" during the SNP's time in power at Holyrood, before adding that this "explains why Andy Burnham is so obsessed with John Swinney and the Scottish National Party". He will say the Labour leader "understands that, for as long as the binds of their Union continue to burst at the seams, there is no possible way that any UK prime minister can seriously survive".
Scottish Labour deputy leader Dame Jackie Baillie said: "This is nothing more than a distraction from the SNP, who do not want anyone to focus on their poor record in government. Stephen Flynn and the SNP could set out their plans for fixing our NHS, restoring our education system, or improving our public services but, instead, they want to go back to the division of 2014. The people of Scotland deserve better than the narrative of grievance pushed by the SNP. They deserve a government focused on the issues that matter most to people across Scotland, not constantly seeking constitutional fights."
