Disgraced US financier Bernie Madoff says he is undergoing weekly psychiatric therapy sessions in prison, where he has learned he is a "good person" despite swindling investors out of billions of dollars.

Madoff, 72, serving a 150-year sentence after pleading guilty in March 2009 to orchestrating what is considered the biggest Ponzi scheme in history, conducted a phone interview from prison with New York magazine writer Steve Fishman.

Fishman's account of the interview was posted online on Sunday, along with portions of recordings Fishman made of their conversation, which ran for several hours over the course of more than a dozen phone calls.

Madoff denied his actions were motivated by a desire for greater wealth or a better lifestyle. He said he engaged in the massive, long-running fraud because it fed his ego to have large banks wanting to invest their money with him.

Madoff also discussed the effect on his family from the suicide of his eldest son, Mark, 46, in December, on the second anniversary of his father's arrest.

And he also described examining his own character in sessions with a therapist at the North Carolina prison where he is incarcerated. Madoff said he asked the therapist whether he was a sociopath, as some have suggested, and that she told him he was not because he felt remorse for his actions.

"I am a good person," Madoff was quoted as telling Fishman.

Prosecutors have estimated Madoff's scheme took in about $65 billion over at least two decades, but a court-appointed trustee has estimated the losses at about $20 billion.

Madoff said his scheme began in earnest in the early 1990s, when he had large amounts of capital and not enough to invest in, according to the New York magazine article.

"I had more than enough money to support any of my lifestyle and my family's lifestyle. I didn't need to do this for that. I allowed myself to be talked into something, and that's my fault," Madoff said.

He recounted dipping into money from investors' capital to pay out solid returns to other investors, leading major banks to start paying attention and wanting to invest with him.

"It feeds your ego. You say to yourself, 'All right, all of a sudden, these banks, which wouldn't give you the time of day, some of them, all of a sudden they're willing to give you a billion dollars'," he said.

Madoff's sons, Mark and Andrew, ran the brokerage at their father's firm. On last Dec 11, Mark committed suicide by hanging himself.

Madoff said the last time he saw his sons was when he confessed to them his wrongdoing before his arrest. And Madoff said his wife was devastated by his son's suicide.

"How could she not be angry at me?" Madoff asked. "She tries not to be, but it's hard not to be. I mean, you know, I destroyed our family," he said.