Ann Widdecombe predicted a “sea change in British politics” with the rise of insurgent party Reform UK.
The ex-Tory minister said her former party is “rattled and despairing” amid ongoing speculation of plots to replace Rishi Sunak.
She added that the Conservatives were focusing on “rubbishing” the rebranded Brexit Party rather than asking why voters are switching.
Writing in her Daily Express column, she said: “The Tories are both rattled and despairing, not without cause. So what do they do? Produce some eye-catching new policy? No.
“They mutter on about changing the leader yet again, unable to see that all that would achieve is yet more division and public ridicule.
“In a situation where Labour is miles ahead and looking at a landslide victory, do they focus on the enemy charging right at them?
“No, they pour all their efforts into rubbishing Reform without even stopping to ask why people are so attracted to its new broom or why voters are so thoroughly fed up that they are deserting the major parties.
“In short they focus on the messenger not the message, which is causing their problems.
“Their current chaos has many roots: the sharp decline in quality of MP resulting in benches packed with panickers and plotters, a dearth of new ideas, the escalating triviality of press and media and the staleness of a long-term of office together with a desertion of core values such as freedom of speech, common sense, control of our porous borders and proper maintenance of our armed services.
“About every 100 years or so there is a sea change in British politics, as happened for example in 1900 with the formation of the Labour Party. It is happening again with the challenge presented by Reform.”
Ms Widdecombe, a former Brexit Party MEP and member of Reform UK, insisted Labour will win the next general election either with a “big majority or a vast one”.
She said: “Starmer is not responsible for that – the Tories are. The only answer is to break the mould and vote for change.
“The other day I commented sadly to a former colleague that I could not believe what had happened to the party to which I had given 55 years of my life.
“He replied: ‘It has gone. The party we knew and served simply isn’t there any more. It died years ago.’
“He is totally right. RIP the once mighty Conservative Party, but at least there is a phoenix rising from the ashes… and it is called Reform.”
Ms Widdecombe’s comments come as Reform UK last week hit a record 16% in a national poll.
The party gained its first MP last month with the defection of Lee Anderson from the Tories in an Islamophobia row.
Reform, currently led by businessman Richard Tice, is likely to be further boosted if honorary president Nigel Farage makes a comeback.
