It comes as it emerged a radical “flat tax” that would have seen all workers pay only 20 per cent was considered for their autumn statement which sparked economic and political turmoil.
One year on from Ms Truss’s spree of unfunded tax cuts, the former PM is set to launch an astonishing attack on Rishi Sunak’s government – claiming it has spent £35bn more than she would have if she had remained at No 10.
The short-lived premier will use a speech on Monday to defend her time in charge, nearly a year on from the ill-fated mini-Budget that helped end her premiership after only six weeks.
In his most frank interview yet, Mr Kwarteng questioned Ms Truss’s temperament and claimed she would have “blown up” something – even if the pair had escaped the mess of the autumn statement.
“I love her dearly, she’s a great person, very sincere and honest,” he told the Telegraph’s political editor in a new book. “But if it hadn’t been the mini-Budget, she would have blown up on something else.”
The former chancellor added: “I just don’t think her temperament was right. She was just not wired to be a prime minister.”
Mr Kwarteng revealed in a new book by Ben Riley-Smith, The Right to Rule, that he thought his sacking by Ms Truss only six days before her own exit was “completely insane”.
Summoned to her office after a trip to Washington DC amid economic turmoil, Ms Truss was said to be in tears at having to fire him. “They’re going to come after you now,” Mr Kwarteng said.
He added: “They’re going to ask you: If you’ve sacked him for doing what you campaigned on, why are you still there?”
Told Jeremy Hunt was going to replace him, Mr Kwarteng fumed: “Hunt?! He’s going to reverse everything!” Before leaving he told the PM: “You’ve got three weeks.”
It also emerged that the Truss government considered a radically right-wing proposal for a flat tax on income of 20 per cent, submitted by the then business secretary Jacob Rees-Mogg. The idea was reportedly referred to as “full Estonia” by senior Tories – but was rejected by Mr Kwarteng.
Despite a fresh round of scrutiny and criticism of the mini-Budget, Ms Truss is set to defend her ideas at a speech at the Institute for Government and criticise Mr Sunak’s economic policy.
Ms Truss will reportedly point out that under her plans £18.4bn would have been saved in 2023-24, with another £17.1bn in 2024-25.
She will claim the PM was wrong to put more into public services since taking office and will say she wanted to save money by increasing benefits with wages rather than the higher rate of inflation.
“Even those modest savings did not command the support of the parliamentary party,” Ms Truss is expected to say. “It is a very serious issue for those of us who want to see smaller government that currently making significant changes to spending simply doesn’t have enough political support.”
The comments are set to spark another round of infighting, with some on the Tory right keen to see spending cuts to pay for tax reductions.
Andy Street, the influential Tory mayor of the West Midlands, warned Mr Sunak against the idea of a real-terms cut to benefits – thought to be under consideration. He told The Observer a rise in line with inflation “has to happen again because that’s a real symbol”.
Meanwhile, Labour said Britain’s homeowners have taken a hit of more than £300bn in the year since the Truss mini-Budget.
The party pointed to a fall of around 5 per cent in house prices since September 2022, saying it meant UK households have seen £336bn wiped off the value of their property in the last year.
Pat McFadden, shadow Cabinet Office minister, said families continued to suffer “thanks to Liz Truss and Kwasi Kwarteng’s disastrous casino economics”.