Liz Truss is a “symptom of the dysfunction at Westminster – not the cause”, SNP depute leader Keith Brown will tell delegates at the party’s conference.
Mr Brown will take aim at Westminster in his speech, which will open the first in-person SNP conference since before the pandemic in Aberdeen on Saturday.
He will also speculate on whether Conservative MPs will “force out” the Prime Minister soon.
“She has delivered more chaos and confusion than even the most pessimistic prediction,” he is expected to tell delegates.
“In less than a month, she has tanked the economy; risked the pensions of millions; scrapped the cap on bankers’ bonuses; announced and then U-turned on income tax cuts for the wealthy; created a debt crisis; and showed the world she is singularly unfit for the job.
“The chaos she has created is no surprise.
“She has been a Tory Government minister for a decade, serving under Cameron, May and Johnson. From austerity to Brexit, she’s been complicit in inflicting the worst Tory policies on the people of this country.
“It is a sobering thought indeed that when the history of 2022 is written, it will record that Boris Johnson was not even the worst prime minister this year.
“What is clear is that Liz Truss is a symptom of the dysfunction at Westminster – not the cause.
“The very fact that she and her policy agenda was deemed acceptable to enter Downing Street in the first place speaks volumes.”
Mr Brown will also condemn Labour, describing leader Sir Keir Starmer as “just another Tony Blair” and accusing the party of being “as Trumpian as the Tories in their denial of Scottish democracy”.
He will tell delegates: “It is an incontrovertible fact that the SNP has a cast-iron mandate to hold an independence referendum.
“But Labour always side with the Tories to protect Westminster control – no matter how high a price the people of Scotland pay.
“Labour supports the deeply damaging Brexit that Scotland did not vote for.
“I repeat, Labour supports Brexit, and stands against any Scottish aspiration for our country to re-join the European family of nations.
“And never forget, never forgive, that in 2014 it was Labour who championed the No campaign message that only a No vote would deliver economic stability.
“It seems absurd now, but that’s what Labour promised. They can’t be trusted with our future.”
Mr Brown will also seek to paint UK politics as cyclical, with Labour taking over from the Tories before eventually ceding Number 10 back to the Conservatives, and he will insist “homes, pensions and incomes “are not safe under Westminster control”.
Scottish Labour deputy leader Jackie Baillie said Mr Brown’s speech will lay out “in black and white” that “the SNP do not care whether the next UK government is run by the disastrous Tories or a reforming Labour government”.
“It is clear for all to see that the SNP’s claim to be a progressive party is a sham. They don’t care about kicking out this disastrous Tory government, all they care about is their narrow nationalist obsessions,” she added.
“No amount of spin can hide the SNP’s disastrous governance of this country – or its dangerous stewardship of the NHS.
“Unlike the SNP, Labour is focused on the priorities of the people of Scotland – tackling the cost-of-living crisis and building a fairer, greener and more secure future for our country.”
Scottish Tory constitution spokesman Donald Cameron MSP said: “The SNP are kicking off their conference in the only way they know how – by talking about independence.
“Keith Brown’s speech is the height of self-indulgence to pander to the party faithful. It sets the tone for another SNP conference that will be dominated by independence, rather than talking about the real priorities of Scots.
“People across Scotland want the SNP to focus on supporting households and businesses through the cost-of-living crisis and tackling the problems in our NHS, rather than another divisive referendum.
“Typically those issues have been put on the backburner by the SNP. Instead Keith Brown will use his stage time to highlight the SNP’s relentless pursuit of independence yet again.”