Three WorldCom bosses have been ordered before a Congressional hearing to investigate how the telecom giant inflated its profits by £2.5 billion.

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 influential 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.

He said: "I'm concerned about the economic impact of the fact that there are some corporate leaders who have not upheld their responsibility."

WorldCom already faces a fraud inquiry by the US Securities and Exchange Commission (SEC) after the companies board of directors uncovered £2.5 billion in improperly booked expenses on Tuesday.

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 £2.9 billion.