An array of executives, lawyers, bankers and institutions were formally named on Monday in an amended class action complaint for their alleged role in the Enron scandal.

Lawyers for the Regents of the University of California, the court-appointed lead plaintiff in the case, said the defendants "pocketed billions of dollars" while Enron investors were being defrauded.

Among those on the list are: Andersen, Enron auditors; Enron's banks, including JP Morgan Chase and Citigroup; and Enron's lawyers, including Vinson & Elkins. Enron board members such as Wendy Gramm, wife of the influential Republican senator Phil Gramm, are also named.

"The apparent success of Enron was a grand illusion -a false picture created by manipulative devices and contrivances," the lawsuit says.

The banks, it alleges, made vast profits from an energy trader that had become "the golden goose of Wall Street".

"The scheme to defraud Enron investors was extraordinary in its scope, duration and size . . . It was designed and/or perpetrated only via the active and knowing involvement of Enron's general counsel . . . accounting firm . . . and Enron's banks."

The lawyers, headed by class-action specialist Milberg Weiss, allege the banks took part in fraud as they underwrote Enron's debt issues and lent money, so allowing the energy trader to continue to operate.

JP Morgan Chase, which was added back in to the list of defendants over the weekend in last-minute amendments, is heavily criticised in the lawsuit.

"There was no so-called 'Chinese wall' to seal off the JP Morgan securities analysts from the information which JP Morgan obtained rendering commercial and investment banking services to Enron," it says.

JP Morgan Chase declined to comment on Monday. Merrill Lynch, another of the banks named in the suit, said: "We believe there is no basis for this claim and we intend to defend vigorously against it."

Legal experts say it will be a hard case to prove against the banks. Wall Street cannot be liable simply for assisting in any alleged fraud by ignoring warnings, however blatant. Lawyers would have to show that the banks were "primary violators".

Andersen has offered to settle its part in the case for $300m, reduced from its initial $750m offer and indicative of its dire financial circumstances brought on by deserting clients and disintegrating worldwide structure.

Enron's auditors failed to cut a deal in time to be removed from the suit, but are still hoping to resolve the problem soon. Joseph Berardino, Andersen's former chief executive who resigned over the issues, is named as a defendant.