Scottish nationalists are "changing the packaging" to try and revive their failing bid for independence, Michael Moore is expected to say later.
The Scottish secretary will use a speech in Glasgow to claim the struggling pro-independence campaign, which only enjoys support from around 35% of voters, is forcing the SNP to redefine its goals ahead of next year's poll.
"When it comes to their rhetoric about an independent Scotland, the SNP has retreated a long way in a short time," Moore is expected to tell an IPPR audience at Glasgow University.
"They no longer want to talk about how different things would be, they want us to believe instead that so much could stay the same."
His speech prompted an angry reaction even before it was delivered, with deputy first minister Nicola Sturgeon dismissing Moore as belonging to a coalition which had "walked away" from its commitments in Scotland.
"At the heart of this campaign is the reality that the people of Scotland benefit most when decisions about Scotland are taken in Scotland," she insisted.
"Whatever the no campaign say the evidence is crystal clear."
She argued the SNP government had already secured free higher education north of the border and prevented the "creeping privatisation of the NHS", while warning that without a 'yes' vote nuclear weapons will remain in Scotland and households will face further cuts to their budgets.
Moore's speech will take a broader look at the SNP's campaigning message by pointing out how the nationalists' message has shifted in recent years, however.
"The team who once argued that we should be 'Free by 93' now campaign for 'an interdependent United Kingdom of five unions'," he will add.
"The Scottish National party hasn't campaigned for 80 years and governed for six to strengthen or preserve the United Kingdom.
"Having looked at the numbers, the SNP leadership has come to fear that independence is a product too few Scots are willing to buy; so to sell the goods, they are changing the packaging."
He will highlight the SNP's enthusiasm to remain in Nato while opposing nuclear weapons and its acceptance of the need to retain the pound - a reversal of its previous position.
"Scotland is more than wealthy enough to be a fairer and more prosperous society," Sturgeon added.
"It is only with full responsibility in Scotland following a yes vote and independence that we will truly be able to protect the people of Scotland by taking decisions for Scotland, in Scotland."
Campaigning ahead of the referendum appears to have entered a new phase as pollsters accept the 'no' campaign is facing an uphill struggle.
American polling guru Nate Silver told the Edinburgh Book Festival earlier this month he believed the outcome was now all but certain.
"For the most part it looks like it's a question of how much the 'no' side will win by, not what the outcome might be," he said.
"If there was a major crisis in England – if the eurozone split apart and there were ramifications economically then maybe things would be reconsidered a little bit."
Scottish voters will be asked "should Scotland should be an independent country?" on September 18th 2014.