New York ? WorldCom Inc., the long-distance giant accused of falsifying its books by $11 billion in the biggest accounting scandal in U.S. history, agreed Monday to pay investors $500 million to settle civil fraud charges.

The fine would be one of the largest the Securities and Exchange Commission has ever imposed. The settlement was presented to U.S. District Judge Jed Rakoff, who said he would not rule before June 11.

The judge said he needs to learn “much more of the defendant’s seemingly massive fraud,” who would be affected by the settlement and what internal controls WorldCom has put in place.

The settlement actually calls for WorldCom to be fined $1.51 billion, an amount that would be reduced to $500 million as part of the company’s Chapter 11 bankruptcy case.

WorldCom, which wants to change its name to MCI, was accused of misleading investors by falsifying its books to hide expenses and inflate earnings. The SEC and WorldCom had been negotiating for months, and the deal would be important to WorldCom’s hopes of emerging from bankruptcy as early as September.

A group of former WorldCom employees critical of the company denounced the accord as a “slap on the wrist.” The $500 million is equivalent to “about one week of revenue … an insignificant amount by any standard,” said the group, BoycottMCI.com.

The group’s founder, Mitch Marcus, said the accounting scandals that brought down Enron Corp. and the accounting firm Arthur Andersen “pale in comparison” to “the degree of illegality” at WorldCom.

The SEC sued WorldCom last June, just a day after the company disclosed $4 billion in financial misstatements, shocking a market already buffeted by the Enron scandal. Since then, WorldCom has raised the estimate to around $7 billion, then $9 billion and eventually $11 billion.

The SEC broadened the scope of its civil case in November to allege that WorldCom misled investors starting at least as early as 1999, years earlier than previously alleged. WorldCom executives then agreed to submit to ethics training, and the duties of the company’s court-appointed watchdog were expanded.

While the SEC pursued civil charges, the Justice Department has been conducting a criminal investigation and has charged several former executives.

WorldCom’s ex-controller, David Myers, and its former chief financial officer, Scott Sullivan, were arrested in August. Federal prosecutors say the two directed employees to conceal more than $3.8 billion in expenses in financial reports, causing WorldCom earnings to be overstated by $5 billion.

Myers pleaded guilty and is cooperating with prosecutors in the criminal probe. Sullivan — the nation’s highest-paid CFO in 1997, earning $19 million — has denied any wrongdoing. He is free on $10 million bail.

Three other WorldCom executives have pleaded guilty to federal charges.

Ousted WorldCom CEO Bernard Ebbers, who has not been charged, last month failed to make his first payment of around $25 million on more than $400 million in loans that he owes the company.

WorldCom was among the fastest-growing and most aggressive players in the late 1990s telecom and Internet boom. After being hurt by the wider telecom industry slump and ravaged by its own accounting scandal and bankruptcy, WorldCom cut its work force to 55,000 from a peak of 80,000. It remains second only to AT&T Corp. in the long-distance market and is a major carrier of data over the Internet.

In addition to changing its name to MCI to reduce the taint associated with WorldCom, the company also plans to move its headquarters from Clinton, Miss., where WorldCom was founded, to Ashburn, Va., near MCI’s base in the suburbs of Washington, D.C. It hired a new CEO and chairman, former Compaq Computer Corp. chief Michael Capellas, in November.