Former Enron executive Michael Kopper has pleaded guilty to fraud charges and is expected to point the finger at ousted chief financial officer Andrew Fastow in the first indictment arising from the company's collapse.

Kopper has been charged with conspiracy to commit money laundering and conspiracy to commit wire fraud, while serving as Fastow's right hand man at Enron. He agreed to cooperate with prosecutors in Houston as part of a plea bargain deal and was released on $5m bail.

Kopper worked in Enron's global finance unit and played a major part in the formation of off-balance sheet partnerships, largely financed by company shares and used to hide $1bn of debt.

Enron was one of several companies, including WorldCom and Adelphia Communications, whose certification statements issued to the SEC were rejected outright after they admitted that they could not testify to the accuracy of their results.

Adelphia's founder John Rigas and other members of his family were arrested on charges of criminal fraud and taken to court, while the company has managed to complete a $1.5bn debtor in possession loan with 12 banks and about 30 funds participating.

Investigators at WorldCom managed to unearth a further $3.3bn worth of fraudulent transactions, relating to legal fees and reserves for bad debts which were treated as income. The total value of fraud is now estimated to be more than $7bn.