Peter Madoff, who pleaded guilty to aiding Bernard Madoff’s fraud while claiming he didn’t know his older brother was running a vast, decades-long Ponzi scheme, was sentenced to 10 years in prison.

U.S. District Judge Laura Taylor Swain yesterday sentenced Peter Madoff after considering pleas from victims of the fraud that she not show him any mercy. As part of an agreement with prosecutors, Madoff agreed not to seek less than the maximum 10- year prison term allowed by law.

In a 55-minute hearing in Manhattan, Swain said the notion that Peter Madoff didn’t know about the wide-ranging fraud at firm is “frankly, not believable.” She urged him to cooperate with investigators who are trying to unravel the Ponzi scheme at his former firm.

“I challenge you to be honest about all that you have done and all that you have seen,” Swain told Madoff before pronouncing sentence.

Peter Madoff, 67, becomes the second person sentenced in the fraud at Bernard L. Madoff Investment Securities LLC, which was exposed in December 2008. Bernard Madoff, who admitted masterminding the scheme, is serving a 150-year sentence in a North Carolina federal prison.

‘Deeply Ashamed’

“I am deeply ashamed of my conduct and have tried to atone by pleading guilty and forfeiting all my assets,” Madoff told Swain. “I am here to accept my punishment from this court.

Swain also sentenced Madoff to one year probation when he’s released and she approved a forfeiture order that Madoff agreed to under which he must surrender all his assets, including Social Security proceeds, up to $143.1 billion. Swain approved the arrangement, which she called ‘‘draconian,’’ saying it ‘‘seals Peter Madoff’s financial ruination.’’

Peter Madoff had asked the court to let him attend his granddaughter’s bat mitzvah next month before he’s ordered to report to prison. At Madoff’s request, Swain said she will recommend he serve his time in a federal prison camp in Otisville, New York, about 70 miles (112.6 kilometers) northwest of New York City. He must report to prison by Feb. 6 at 2 p.m., she said.

Madoff and his lawyers didn’t respond to questions after the hearing. He walked silently through a crowd of photographers and television cameras outside the U.S. courthouse in lower Manhattan, then stepped into a silver BMW sedan and was driven off.