The Conservative MP, who is releasing a book called Ten Years to Save the West, argued that the left had infiltrated public and private institutions in “the deep state” and sabotaged her efforts to cut taxes and reduce the size of government.

Truss was forced out of office by her own party after her chancellor presented a budget of £45bn in unfunded tax cuts, which unleashed economic chaos, sent interest rates soaring and caused people to pay more for their mortgages.

Jonathan Ashworth, the shadow paymaster general, said Sunak should address Truss’s comments and take action. “After crashing the economy and sending mortgages rocketing, Liz Truss is now spreading conspiracy theories with Steve Bannon and spearheading a wacky fringe group to take over the Tory party again.

“If Rishi Sunak had any backbone he would stand up and take action against her and Tory MPs indulging this sort of damaging nonsense.

The Liberal Democrats called for Truss to give back the £115,000 allowance for post-ministerial life she was given after leaving office.

“This Conservative party love-in for rightwing American politics is like watching a slow-moving car crash. These bizarre conspiracy theories pedalled by Truss and her cabal should have no place in British politics. Blue wall voters will run a mile from this nonsense,” said Daisy Cooper, the party’s deputy leader.

“Liz Truss was never fit to be prime minister and certainly is not fit to be given a six-figure allowance of taxpayers’ money. It represents another slap in the face to all those paying hundreds of pounds more a month on their mortgages due to her disastrous policies and should be stripped immediately.”