Ex-Culture Secretary Nadine Dorries continues to maintain that Boris Johnson is "one of the world's best leaders" - and didn't rule out returning to government if her old boss comes back.
Since Liz Truss became PM, the party's popularity has surged to new lows, with numerous polls showing Labour taking a record lead after a buoyant conference in Liverpool last week.
Ms Dorries, who is one of the many big names to stay away from the Tory party conference in Birmingham, stopped short of attacking Mr Johnson's successor - claiming markets had "pretty dramatically overreacted".
But she maintained that Mr Johnson, who resigned after a mass walkout of more than 60 Tory MPs at the start of July, said that many voted for him rather than for the party.
The backbencher, who describes herself on Twitter as a "recovering secretary of state", warned Ms Truss not to take her support for granted, telling the Sunday Times : "Liz has my absolute support, but I think if they started reversing some of the achievements that we’ve made in the past year, that support will be tested to the limit.”
She told the newspaper that the shamed former Prime Minister, whose three years and 44 days in office were dogged by scandal, is "definitely having a nicer life at the moment.
But she was tight-lipped when asked if she would take up a frontbench role if Mr Johnson takes the helm again.
Speaking from her home in the Cotswolds, Ms Dorries, 65, said that she feels "quite sorrowful and disappointed about how I think we removed one of the world’s best leaders".
The ardent loyalist, who remained at her boss's side while dozens of Tories finally had enough, claimed some within the party "behaved very badly", and said she would find it "very difficult" to continue working in a positive way after his departure.
Ms Dorries, who backed Ms Truss in the leadership election and sparked ire among the Tory faithful when she aimed a dig at rival Rishi Sunak over his expensive attire, bragged that the Tories were just five points behind in the polls when Mr Johnson departed.
A bombshell YouGov poll this week suggested Keir Starmer's Labour has an eye-watering 33 point lead after Ms Truss and Kwasi Kwarteng's mini-budget sparked chaos.
She claimed Mr Johnson was "the only one that was going to maintain a stable poll position", saying it was "clear that people voted not always for the Conservatives — they voted for Boris".
But despite her loyalty to the previous government, she resisted taking a swipe at the new leadership, telling the newspaper: “The markets had known for two months that Liz was going to introduce £40 billion of tax cuts because it’s exactly what she said she was going to do in her leadership hustings time after time after time, so they knew precisely what was coming..
“I think the markets have pretty dramatically overreacted.”
She said she is now resting up after working "seven days a week and 15 hours a day" during her tenure as Secretary of State, which lasted nearly a year.
Ms Dorries - who has represented Mid Bedfordshire since 2005 - said she would "literally crash out" when she did get time off.
Earlier today Ms Truss acknowledged mistakes over the mini-budget - but said she is standing by her tax-cutting plan as she refused to rule out public spending cuts.
The Prime Minister admitted she could have done more to prepare the ground for Kwasi Kwarteng's financial statement, which spooked the markets, sent the pound plummeting, and forced a £65 billion intervention by the Bank of England to restore order.
Ms Truss said the mini-budget's most controversial measure - the abolition of the 45% tax rate on earnings over £150,000 - was not discussed with the Cabinet but was a decision made by the Chancellor.
As the Conservative Party conference gets under way in Birmingham, Ms Truss faces a difficult task in reassuring the markets and Tory members unnerved by the market turbulence and opinion poll crash suffered since she took office.
"I do want to say to people I understand their worries about what has happened this week," she told the BBC's Sunday With Laura Kuenssberg.
"I do stand by the package we announced and I stand by the fact we announced it quickly, because we had to act.
"But I do accept we should have laid the ground better... I have learnt from that and I will make sure that in future we do a better job of laying the ground."
