By Jonathan Stempel

NEW YORK (Reuters) - The former director of operations at Bernard Madoff's investment firm was indicted by a federal grand jury on securities fraud, conspiracy and other charges related to the largest Ponzi scheme on record.

Daniel Bonventre, 63, faces a maximum of 82 years in prison plus a fine under Wednesday's nine-count indictment, said the office of U.S. Attorney Preet Bharara in Manhattan.

Prosecutors have contended that Bonventre concealed the scope of Madoff's estimated $65 billion fraud, and diverted at least $750 million of investor money to support the trading business at Madoff's firm.

"The charge against Daniel Bonventre is a prosecutorial Hail Mary," his lawyer Andrew Frisch said in an interview. "He is absolutely innocent, and we are looking forward to the trial."

Bonventre's indictment was announced a week after two former computer programmers at Bernard L. Madoff Investment Securities LLC, Jerome O'Hara and George Perez, were indicted on charges of conspiracy and falsifying records.

Six people affiliated with Madoff's firm have been charged. Madoff, former chief financial officer Frank DiPascali and former accountant David Friehling have entered guilty pleas.

An arraignment for Bonventre is scheduled for Thursday morning. Bail was set at $5 million after the defendant was arrested on February 25 at his Manhattan apartment. Bonventre also faces related SEC civil charges.

Prosecutors said Bonventre began working for Madoff's firm in 1968 and was director of operations from at least 1978 until the firm collapsed in December 2008, when Madoff was arrested.

Bonventre was charged with one count of conspiracy, two counts of falsifying records, one count of securities fraud, one count of making a false U.S. Securities and Exchange Commission filing and four counts of filing false tax returns.

The government on Wednesday joined O'Hara's and Perez's case with that of Bonventre. O'Hara and Perez each face a potential 30 years in prison.

When he pleaded guilty last March, Madoff said his firm's market making and proprietary trading operations were legitimate.

Madoff is serving a 150-year sentence in a North Carolina federal prison. Prosecutors have requested "extraordinary" leniency for DiPascali because of his help in the unraveling the case.

The case is U.S. v. Bonventre et al, U.S. District Court, Southern District of New York, No. 10-cr-00228.

(Reporting by Jonathan Stempel; Additional reporting by Grant McCool; Editing by Bernard Orr and Steve Orlofsky)