Tory MP Nadine Dorries has branded George Osborne "stupid" and accused him of lying about her.
She said the Chancellor was out of his depth and a "pernicious influence" on the economy and David Cameron.
Ms Dorries said in a web interview there was a "personal element" to some of her criticisms after the Prime Minister jibed that she was "extremely frustrated" in the Commons last year.
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She said her animosity to Mr Osborne stemmed from his role in defeating a parliamentary amendment designed to restrict abortion counselling.
She said: "He might be a politician and a strategist and a political campaigner. I don't think he's up to the job of being Chancellor."