Federal prosecutors have charged two computer programmers with assisting Bernard Madoff’s $65 billion (£39 billion) fraud and hinted that there are more conspirators to be unmasked.

Jerome O’Hara, 46, from New York, and George Perez, 43, from New Jersey, face 30 years in prison if convicted of conspiracy, falsifying the books and records of a broker dealer, and falsifying the books and records of an investment adviser.

The charge sheets against the men allege that the defendants worked with “others known and unknown” to make Madoff’s giant fraud possible. So far only Madoff himself, his aide, Frank DiPascali, and accountant, David Friehling, have been charged over the Ponzi scheme, which ran for at least 20 years and cost thousands of people their life savings.

The Securities and Exchange Commission (SEC), the US regulator, also brought civil charges yesterday against Mr O’Hara and Mr Perez.

Preet Bharara, the US Attorney for the Southern District of New York, alleged that Mr O’Hara, who worked for Bernard L Madoff Investment Securities from 1990, and Mr Perez, who joined in 1991, created computer programs that were filled with false information such as fake trades and invented counterparties.

Using one main computer called House 17 within Madoff’s Manhattan offices, the programmers also hid the names of some of Madoff’s clients.

The programs were used by Madoff and DiPascali to deceive the SEC along with an unnamed European accounting firm during at least five reviews of his Manhattan firm, Mr Bharara alleged.

George Canellos, director of the SEC’s New York regional office, said: “Without the help of O’Hara and Perez, the Madoff fraud would not have been possible.”

In return, Madoff gave DiPascali orders to pay the men “whatever they wanted to keep them happy”, the US Attorney alleged.

In April 2006 the two programmers appeared to have what the SEC described in its charges as a “crisis of confidence” in which they deleted 218 of the 225 fraudulent programs from House 14.

At the same time, Mr O’Hara withdrew almost $1 million of his own money that was invested with Madoff, and Mr Perez withdrew almost $300,000.

In September they met Madoff and told the swindler that they would not continue to lie for him, the US Attorney said.

FBI agents found handwritten notes in Mr O’Hara’s desk that read: “I won’t lie any longer. Next time I’ll say ‘Ask Frank’, ” in an apparent reference to DiPascali.

Madoff gave the men a 25 per cent pay rise and a bonus of $60,000 each to convince them to continue to assist the scam, according to the criminal charges.

DiPascali pleaded guilty to ten criminal counts in August and is assisting investigators in the hope of receiving a lighter sentence. He faces up to 125 years in prison.

Friehling pleaded guilty this month and is also assisting the investigation in the hope of receiving less than the 105-year maximum sentence.

Madoff is serving 150 years in the Butner Federal Correctional Complex in North Carolina for perpetrating the world’s largest investment scam.

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