Three WorldCom bosses have been ordered to testify at a Congressional hearing to investigate how the telecom giant inflated its profits by €3.8bn.
Sacked chief financial officer Scott Sullivan and current chief executive John Sidgmore have been subpoenaed by the House Financial Services Committee.
Former chief executive Bernard Ebbers and Wall Street analyst Jack Grubman, who promoted the company's stock, have also been ordered to face the July 8 hearing after the phone company was accused of fraud.
The news came as US President George W Bush warned about the potential economic consequences of the latest accounting scandal to rock corporate America.
"I'm concerned about the economic impact of the fact that there are some corporate leaders who have not upheld their responsibility," he said.
WorldCom already faces a fraud inquiry by the US Securities and Exchange Commission (SEC) after the company's board of directors revealed €3.8bn in improperly-booked expenses on Tuesday.
The firm is the latest in a line of US companies to be struck by accounting scandals that have shaken public faith in corporate America.
Enron collapsed last year in what was the biggest bankruptcy in US history amid revelations that it kept millions of dollars in losses off the books through shady accounting practices.
WorldCom grew rapidly during the last two decades to become one of the world's biggest "backbone" networks for Internet traffic, with 85,000 employees across the globe and 2001 sales of €36.3bn.
But the company, which is reeling from a low stock price, a crumbling telecoms market and an ongoing SEC investigation, is now in serious risk of bankruptcy. It is thought to owe creditors about €4.4bn.