CHICAGO (Reuters) - Author James Frey confessed to Oprah Winfrey on Thursday that he made up details about every character in his memoir "A Million Little Pieces" and the talk show host apologized to her viewers, saying she felt "duped."

"I have been really embarrassed by this," said Winfrey, whose praise for Frey's book in September helped make it the top-selling book on nonfiction lists in the United States last year.

"I really feel duped," she told Frey on her television show. She said he had betrayed millions of viewers.

At one point early in the interview Frey said he still viewed the work as a memoir, not a novel. By the show's end Winfrey made him admit he lied.

"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," he said. "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 began by apologizing to viewers for a telephone call she made to CNN's "Larry King Live" show on January 11, while King was interviewing Frey about the controversy. In the call Winfrey said that even though the facts were being questioned, the book "still resonates with me" and called the controversy "much ado about nothing."

"I regret that phone call," she told her viewers on Thursday. "I made a mistake and I left the impression that the truth does not matter and I am deeply sorry about that. That is not what I believe."

Sitting with Frey in side-by-side easy chairs, Winfrey quizzed the author point-by-point about his book that described his drug-and-alcohol addiction and the people hurt by it.

"All the way through the book I altered details about every one of the characters," Frey said, to disguise true identities.

He spent two hours in jail, not 87 days, and the account of his breaking up with a woman who later committed suicide happened in a much shorter period of time, with their separation occurring while he was taking care of personal business in North Carolina, not while he was in jail, he said.

She committed suicide by slashing her wrists, he said, not by hanging herself.

The controversy over Frey's work has raged for weeks at a level rarely seen in U.S. literary circles, and the debate has even called into question the veracity of other memoir-like works published over the years.

Nan Talese, editorial director from Random House's Doubleday division, which published the book, appeared after Frey and told Winfrey the book went through the usual review process and "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," she said, but "people do not remember the same way. And I thought, as a publisher, this is James' memory of the hell he went through and I believed it."

Asked if The Smoking Gun Web site, which first questioned the book, had accurately characterized the discrepancies, Frey said "I think most of what they wrote was pretty accurate," adding they did "a good job."

Frey said he had developed an image of himself for the book as "being tougher than I was, badder than I was" as a "coping mechanism."

Winfrey asked if that was to make a better book or to make him a better person.

"Probably both," he answered.

Frey's book had been chosen by Winfrey for her reading club -- an honor which often turns books into best sellers. The book sold more than 1.77 million copies last year after being chosen by Winfrey.

On January 17 Winfrey chose Holocaust survivor Elie Wiesel's "Night" as her latest selection, sending the book, first published in the United States in 1960, to the top of best-seller lists.

Random House is a unit of German media conglomerate Bertelsman AG.