Prosecutors - who called for a life sentence - charged that Bennett hid losses by his firm and its customers from its auditors and investors.
Bennett cried when he spoke to the court, saying: "I knew failing to disclose these filings was wrong. I know I was wrong. I deeply regret it."
He added: "I take full responsibility for my actions and would like to apologize to my family and all those who were harmed by my conduct."
As the Gladstone, N.J., resident left court, he declined to comment. His lawyer, Gary Naftalis, said: "Mr. Bennett has candidly acknowledged his involvement in the matter. He was forthcoming and candid and wants to put this matter behind him."
Prosecutors said federal sentencing guidelines call for a sentence of life in prison, an outcome they said was likely given Bennett's age. The British citizen faces a maximum of 315 years in prison; his sentencing was set for May 20.
Bennett must also turn over $2.4 billion in assets to the government, prosecutors said.
Prosecutors also called for Bennett to be jailed immediately, saying that the $50 million bail he had already posted was insufficient, but Buchwald said she would not immediately jail him. He remains confined to his New Jersey home by electronic monitoring, though he has been permitted to go to his Manhattan apartment to meet with lawyers.
The judge said the lengthy prison term Bennett may face was not unusual for "any defendant who was older and who was facing sentencing in the post-Enron era."
She added: "The situation was the same for Mr. Bennett - that their residence in prison is possibly the last residence they're ever going to have."
The government said Bennett kept auditors and investors from discovering hundreds of millions of dollars in losses that the then-privately held Refco and its customers had incurred in the financial markets through trading in the mid 1990s while the company was partially controlled by Bennett. It said he then caused the company to make false filings to the SEC.
Refco went public in August 2005. It filed for bankruptcy just weeks later after disclosing that a $430 million debt owed to the company by a firm controlled by Bennett had been concealed. The disclosure caused Refco's stock value to plummet.
A trial in the case had been set for March.
Refco was one of the world's biggest commodities brokerages, employing some 2,400 employees in 14 countries.
