Securities and Exchange Commission enforcement attorneys were in federal court on Friday to seek emergency relief for investors, including an asset freeze and the appointment of a receiver for Madoff's firm, in an alleged $50 billion fraud that could be the largest ever pinned on an individual.

A federal judge granted the agency's request, enabling it to seize the assets of Madoff's 48-year-old company, Bernard L. Madoff Investment Securities.

Federal prosecutors in Manhattan charged Madoff with a single count of criminal fraud, while the SEC accused him of civil fraud.

Madoff, a former chairman of the Nasdaq Stock Market, was influential and his self-named securities firm cut a high profile in Wall Street circles. SEC inspectors would have performed regular inspections of his securities brokerage operations as part of the agency's oversight program.

SEC officials stress that it was Madoff's separate and secretive investment-adviser business that was used to perpetrate the alleged scheme, and that examinations of the securities operations wouldn't necessarily have detected irregularities. The hedge fund business didn't register with the SEC until September 2006.

"If the SEC didn't come in and inspect (the Madoff hedge fund), then they have a hell of a lot to answer for," said James Cox, a Duke University law professor and securities law expert.

Other SEC critics questioned how Madoff could pull off, without the agency's notice, such an audacious fraud that prosecutors said amounted to a giant Ponzi scheme.

"The agency can't help but look bad," said Barbara Roper, director of investor protection at the Consumer Federation of America. "It does raise questions ... about the quality of the enforcement division generally. It's obviously something that the new (Obama) administration has to get to the bottom of."

The SEC said in a statement Friday that staff in its New York office conducted two inquiries — in 2005 and 2007 — into Madoff's company. Inspectors examined the securities brokerage operation in 2005, finding three violations of rules requiring brokers to obtain the best possible price for customer orders. In 2007, enforcement staff completed an investigation and did not refer the matter to the SEC commissioners for legal action, the statement said.

Most recently, as family members turned Madoff in after he confessed his deceit to them, the SEC said, the staff reopened its investigation of his company and the civil fraud action resulted on Thursday.

The SEC wasn't the only regulator to be criticized over the Madoff affair. Bill Singer, a securities lawyer in New York who represents investors and firms, cited the role of the Financial Industry Regulatory Authority, the securities industry's self-policing organization.

The organization, known as FINRA, only has authority to inspect and discipline securities firms and brokers; its jurisdiction doesn't extend to investment advisory firms.