NEW YORK — Raj Rajaratnam, the hedge fund billionaire at the center of the biggest insider-trading case in U.S. history, was sentenced Thursday to 11 years behind bars — the stiffest punishment ever handed out for the crime.

“His crimes and the scope of his crimes reflect a virus in our business culture that needs to be eradicated,” U.S. District Judge Richard J. Holwell said. “Simple justice requires a lengthy sentence.”

The 54-year-old founder of the Galleon Group hedge fund was also fined $10 million and ordered to forfeit $53.8 million in what the judge said were illicit profits from trading on confidential corporate information.

Prosecutors said Rajaratnam made as much as $75 million in all by cultivating a network of friends, former classmates and other tipsters at various companies and investment firms who supplied him with early word on such things as mergers and earnings announcements. In return, they received kickbacks or a chance to get in on the action.

Among the companies he profited from were Google, IBM, Hilton Hotels, Intel, Advanced Micro Devices and Goldman Sachs.

The sentencing was the last major act in a series of prosecutions that followed Rajaratnam’s 2009 arrest. More than two dozen people were arrested in the investigation, nicknamed Perfect Hedge, and all were convicted.

The judge called it “an assault on the free markets that are a fundamental element of our democratic society. There may not be readily identifiable victims, but when the playing field is not level, the integrity of the marketplace is called into question and the public suffers.”

The longest previous sentence in an insider-trading case was 10 years, given twice before. But Rajaratnam’s punishment fell far short of the 24.5 years prosecutors had asked for.

“Today you sentence a man who is the modern face of illegal insider trading,” federal prosecutor Reed Brodsky told the judge. “He is arguably the most egregious insider trader to face sentencing in a courthouse in the United States.”

The Rajaratnam probe relied heavily on the most extensive use of wiretaps ever for a white-collar case. Prosecutors captured conversations in which he and his accomplices could be heard gleefully celebrating their inside information.

At his trial in May, prosecutors said Rajaratnam could convert short telephone conversations into millions in profits. For instance, they said, a 30-minute call with an Intel Corp. insider yielded a $2 million windfall.

Rajaratnam also bought $27 million in Goldman Sachs stock after getting an illegal tip that Warren Buffet was going to pump $5 million into the struggling investment bank.

Printed on Friday, October 14, 2011 as: Hedge fund manager receives longest insider trading verdict