US authorities have charged the brother of fallen hedge fund billionaire Raj Rajaratnam with participating in his insider dealing scam.

Rajarengan Rajaratnam, younger brother of the Galleon hedge fund boss, now lives in Brazil and the US is likely to press for him to be extradited to face the charges. The indictment comes as a deadline to bring charges for securities violations approached.

Rajarengan, 42 and known as Rengan, was mentioned on numerous occasions during his brother's trial in 2011, the largest insider-dealing trial in US history.

Rajaratnam was convicted in 2011 of earning up to $75m illegally from insider tips. He is now is serving an 11-year prison sentence. Rengan Rajaratnam has been charged with conspiracy to commit securities fraud and six counts of securities fraud.

"Along with his brother, Rengan Rajaratnam was allegedly at the heart of an insider trading scheme that swept up an unprecedented number of people in its web of corruption," Manhattan US attorney Preet Bharara said in a statement.

So far the US authorities investigation of the Galleon Group has resulted in more than two dozen convictions, including Rajat Gupta, a former Goldman Sachs director and boss of the McKinsey management consultant. Several former Galleon traders are now cooperating with the authorities.

At trial it emerged that Rengan had been trading in a fund that held shares of tech firm Clearwire ahead of a deal with chip giant Intel. The court heard that Raj Rajaratnam had been given inside information by Rajiv Goel, an Intel employee and former classmate of his at the University of Pennsylvania's Wharton School.

After the Wall Street Journal broke news of the deal Rengan Rajaratnam called his brother. In a conversation taped by the FBI he said: "Oh dude, we're fucked."

"It just hit the Wall Street Journal." He said: "I don't know how much you got in today, but I think it's gonna rip tomorrow."

Raj Rajaratnam's lawyers argued lawyers had taken the conversation out of context. Rengan Rajaratnam's lawyer was not immediately available for comment.