NEW YORK -- Disgraced financier Bernard Madoff should receive a 150-year sentence for orchestrating perhaps the largest financial swindle in history, federal prosecutors said in court papers Friday.

"The sheer scale of the fraud calls for severe punishment," the prosecutors wrote in response to a defense motion seeking lighter punishment.

Madoff, 71, is due to be sentenced Monday after pleading guilty in March to charges that his exclusive investment advisory business was actually a massive Ponzi scheme.

Federal sentencing guidelines allow for the 150-year term, prosecutors said. Any lesser sentence, they added, should still be long enough to send a forceful message and "assure that Madoff will remain in prison for life."

The government's papers quoted from letters to U.S. District Judge Denny Chin written by victims of the scheme who are suffering severe hardships.

Madoff "ruined lives," one letter said. "He deserves no mercy."

At the time of Madoff's arrest, fictitious account statements showed thousands of clients had $65 billion. But investigators say he never traded securities, and instead used money from new investors to pay returns to existing clients.

Prosecutors said Friday that the total losses, which span decades, haven't been calculated. But 1,341 accounts opened since December 1995 alone suffered loses of $13.2 billion, they said.

Madoff attorney Ira Sorkin argued in court papers last week for a 12-year term. He said his client deserved credit for his voluntary surrender, full acceptance of responsibility and meaningful cooperation efforts.

"We seek neither mercy nor sympathy," Sorkin wrote. But he urged the judge to "set aside the emotion and hysteria attendant to this case" as he determines the sentence.

Other court papers filed Friday showed Madoff and his wife Ruth have agreed to sell a $7 million Manhattan apartment where she still lives and forfeit the proceeds. Other property, including an $11 million estate in Palm Beach, a $4 million home in Montauk, N.Y., and a $2.2 million boat, will be put on the market as well.