Glenn Hubbard, an economic adviser to the Romney presidential campaign, said former Treasury Secretary Tim Geithner lied about him in his new book, "Stress Test: Reflections on Financial Crises."

Geithner writes in the book that Hubbard told him in a conversation during the 2012 presidential campaign that "of course we have to raise taxes [if Romney is elected], we just can't say that now."

But Hubbard, dean of Columbia University's business school, denies he ever said that. "[Geithner] is going to go out and say what he wants," Hubbard tells Politico. "It just happens to be a lie."

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"I was asking him something like, how can Romney's plan be off base because it's essentially the Bowles-Simpson structure and Bowles-Simpson actually raises revenue," Hubbard tells Politico. "But I wasn't suggesting that we're trying to raise taxes."

In a statement to CNBC, Hubbard states, "Neither Mr. Geithner nor his publisher reached out to check the veracity of the statement before publication."

But Geithner is sticking to his guns. His spokeswoman, Jenni LeCompte, tells CNBC, "Mr. Geithner's memory on this exchange is crystal clear. He stands by his account."

As for the book as a whole, New York Times reviewer Michiko Kakutani appears to like it. "'Stress Test' provides an intimate take on the financial crisis, and in this respect stands as a gripping, if subjective bookend to already published accounts," she writes.

"The book attempts to explain why Mr. Geithner and his colleagues made the choices they did — something Mr. Geithner acknowledges he 'never found an effective way' of doing at the time."

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