In a dramatic and televised change of heart, Oprah Winfrey yesterday turned on an author whose memoir she chose for her influential book club, but which was subsequently shown to be fabricated.

Winfrey sealed the success of James Frey and his tough, expletive-filled memoir A Million Little Pieces, when she chose the book, a hallucinatory description of Frey's crime and drug-fuelled past, as the autumn selection of her book club last September.

Driven by an emotional interview on Oprah and a website that asked "Has this book saved your life?", A Million Little Pieces was the second biggest selling book in America last year, selling 1.77 million copies. Its sequel, My Friend Leonard, has quickly risen in The New York Times bestseller lists.

But this month, an exhaustive investigation by The Smoking Gun, an American website that prides itself on unearthing public records and mugshots of arrested celebrities, showed that crucial sections of the book had been made up, not least Frey's claim to have spent 87 days in prison. The website disclosed that Frey had spent just a single afternoon in police custody.

Winfrey initially supported Frey - making a surprise phone call to Larry King Live to back her author when he was being interviewed by CNN. But yesterday she brought him on to her show and in front of baying, booing live audience, introduced the author as "Mr Bravado Tough Guy", before taking him to task for a string of inaccuracies.

"I really feel duped," she said. "But more importantly, I feel that you betrayed millions of readers."

Frey, who submitted his book as fiction but eventually had it published as a memoir without a word being changed, defended his work. "I don’t think it is a novel," he said. "I still think it’s a memoir."

But after Winfrey had addressed a series of disputed passages, including Frey's claim to have endured root canal surgery without anaesthetic, the author was more contrite.

"This hasn’t been a great day for me," he said. "I feel like I came here and I have been honest with you. I have, you know, essentially admitted to..."

"Lying," Winfrey interrupted.

"To lying," said Frey. "It’s not an easy thing to do in front of an audience full of people and a lot of others watching on TV... If I come out of this experience with anything it’s being a better person and learning from my mistakes and making sure I don’t repeat them."

Winfrey said she had received hundreds of messages of support for Frey when the first doubts were expressed about his memoir. But she said these had clouded her judgment, leading her to defend him on CNN, saying the controversy was "much ado about nothing".

"I regret that phone call," she said yesterday. "I made a mistake. I left the impression that the truth does not matter, and I am deeply sorry about that. That is not what I believe... To everyone who has challenged my position, you are absolutely right."

Winfrey's frustration extended to the publisher of Frey's work, Nan Talese, who runs a small, exclusive imprint within the US publisher Doubleday.

Hauled on to the stage after Frey, Ms Talese told the audience: "I absolutely believed what I read.... I think this whole experience is very sad. It’s very sad for you, it’s very sad for us."

Winfrey asked how Ms Talese's parent company, Random House, could have described A Million Little Pieces as a "brutally honest and an altering look at... at addiction" without checking whether it was true. Ms Talese replied that the book was checked for libel but not for its basic accuracy.

"Well, that needs to change," said Winfrey.

After the confrontation was aired, Doubleday issued a statement saying it had "sadly come to the realisation that a number of facts have been altered and incidents embellished". It said that printing of the book would be stopped until an author’s note and a publisher’s note had been added.

This afternoon, John Murray, the publishers of A Million Little Pieces in Britain, apologised for "any unintentional confusion regarding the publication of A Million Little Pieces" and said a similar statement would be inserted into UK editions.

A spokeswoman said the publisher was in discussions with Riverhead, the US publishers of My Friend Leonard, over how to describe Frey's memoir of imprisonment, an experience he never had.

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