A document released on October 30 details a prison interview conducted in June by the SEC inspector general in which Madoff says he had the impression that “it never entered the SEC's mind that it was a Ponzi scheme.”

Madoff confided that he didn't bring a lawyer with him when he testified in an inquiry by the SEC's enforcement division because he believed he didn't need one - and he was trying to fool the government investigators into thinking he had nothing to hide.

The details emerged in a summary of inspector general David Kotz's interview with Madoff at the Metropolitan Correctional Centre in New York, released along with hundreds of other documents related to Kotz's extensive investigation of the SEC's failure to detect Madoff's fraudulent scheme for 16 years.

Kotz also issued a statement saying his probe found no evidence to support Madoff's claim of having a “close relationship” with SEC chairwoman Mary Schapiro, who previously headed the Financial Industry Regulatory Authority, the brokerage industry's self-policing organization. Like the SEC, FINRA made periodic exams of Madoff's brokerage operation, which functioned separately from his investment business hidden from regulators' view.

An internal review by FINRA found a regulatory breakdown on the part of the organization in the Madoff case.

Madoff, 71, said in the interview that the SEC examiners ``never asked'' for basic records to corroborate his operations.

The former Nasdaq chairman pleaded guilty earlier this year to charges that his secretive investment advisory operation was a multibillion-dollar Ponzi scheme. He was sentenced to 150 years in prison.