NEW YORK (CNN) -- Alleged swindler Bernard Madoff will plead guilty later this week to 11 counts, including money laundering, perjury and fraud, that could bring a sentence of 150 years in prison, one of Madoff's attorneys, Ira Lee Sorkin, told CNN.

Prosecutors stressed that there had been no plea deal and that Madoff, 70, will have to forfeit any proceeds he accrued from the crimes he is accused of committing.

"The government has not entered into any agreement with Mr. Madoff about his plea or sentencing," said acting U.S. Attorney Lev L. Dassin. "The filing of these charges does not end the matter. Our investigation is continuing."

Earlier, Sorkin and Daniel Horowitz, another Madoff lawyer, told CNN that Madoff was waiving his right to a grand jury indictment and that the defense team had been talking about a plea with government attorneys.

"We obviously have talked to the government," said Horowitz. "And we have been professional with each other."

'No innocent explanation'

Madoff, a former chairman of the Nasdaq stock market and founder of an innovative Wall Street trading firm that electronically matched buy and sell orders, is accused of running a massive fraud in which he allegedly used new investment money from clients to fund for other customers' apparent gains.

It was, "basically, a giant Ponzi scheme," Madoff said, according to the government's criminal complaint.

"There is no innocent explanation," Madoff told two FBI agents, according to the complaint, which states Madoff expects to go to jail.

Madoff was charged in December with one count of securities fraud, which carries a maximum sentence of 20 years in prison. He has remained out on $10 million bail, but is confined to his luxurious Upper East Side apartment.

In court documents, prosecutors said Madoff had run his scheme "from at least the 1980s until his arrest on December 11, 2008, ... by soliciting billions of dollars of funds under false pretenses, failing to invest investors' funds as promised, and misappropriating and converting investors' funds to Madoff's own benefit."

The charges also say Madoff's company, Bernard L. Madoff Investment Securities (BLMIS), claimed that as of Nov. 30, 2008, it held 4,800 client accounts worth about $64.8 billion.

"In fact, BLMIS held only a small fraction of that balance on behalf of its clients," the documents say.

Madoff is scheduled appear at a plea proceeding on Thursday before U.S. District Judge Denny Chin.

Chin also ruled Tuesday that Madoff can keep Sorkin on as his attorney after Madoff said he was satisfied the attorney was representing his interests despite potential conflicts of interest.

Sorkin told the government he invested $18,860 with Madoff in the early 1990s through a retirement account that had been set up with his former law firm that was later transferred to another brokerage firm in 1995. Also, Sorkin's late father held an account with Madoff, the proceeds of which were eventually distributed to trust accounts for Sorkin's two sons.

Sorkin also has represented a Florida accounting firm, Avellino & Bienes, which invested with Madoff.