Edwina Currie, who represented South Derbyshire, said Mr Lewis should "stop using words like 'catastrophe', and instead advise people" on how to deal with their soaring bills.
It comes after Mr Lewis, a consumer finance journalist, called on whoever wins the Tory leadership race - and therefore becomes the next prime minister - to sit down with him for a question and answer session to "ease people's concerns".
Both contenders in the race to replace Boris Johnson - Liz Truss and Rishi Sunak - are being urged to provide more financial support to those struggling most with the cost of gas and electricity.
But Ms Currie, a health minister under Margaret Thatcher, said Mr Lewis should "stop pretending that governments can do everything" "They can't," she added.
But The Money Saving Expert fired back: "It is a catastrophe Edwina!"
He said that while there are steps people can take to help themselves, "energy bills by Jan will cost on avg over half the full state pension & bigger proportion of basic UC. No sensible steps cover that!"
Ms Currie, who forged a career as a writer and broadcaster after leaving politics, was criticised online for the remarks, with one Twitter user calling her "out of touch".
"Edwina . You’re a ‘no nonsense’ , sensible woman, and you really should acknowledge that this situation is a ‘catastrophe’ for many people," another said. "Martin Lewis is not scare-mongering.”
It is not the first time Ms Currie has been criticised for her remarks on fuel poverty. Previously she said that old people who could not afford their energy bills should "wrap up warm".
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