The trustee in charge of recovering money for investors cheated by convicted U.S. financier Bernie Madoff filed suit Wednesday against Swiss bank UBS AG and related parties.

The bank and others collaborated in Madoff's Ponzi scheme, according to the 107-page complaint filed in U.S bankruptcy court.

Trustee Irving Picard, a partner in New York law firm Baker & Hostetler LLP, filed the suit Tuesday. The complete version of the legal complaint is sealed, but an edited version was released to the media Wednesday.

The lawsuit alleges 23 counts of financial fraud and misconduct and seeks to recover at least $2 billion US to be distributed to Madoff's victims, who lost billions when Madoff revealed in December 2008 that his investment company was a gigantic fraud.

Picard has previously filed 20 lawsuits seeking to recover almost $18 billion US in funds from Madoff's family, friends and related companies. He has already recovered roughly $1.5 billion US.

Under U.S. bankruptcy law, Picard has a two-year window to file suit. That window closes next month, on Dec. 11.

In the UBS suit, Picard alleges the bank actively assisted Madoff's scheme by serving as the sponsor, custodian and administrator of various affiliated feeder funds.

The suit names UBS's Luxembourg unit and several feeder funds, including LuxAlpha Sicav, which the unit was responsible for.

LuxAlpha lost 95 per cent of its approximately $1.4 billion US in assets and was dissolved four months after Madoff’s arrest. Liquidators for the fund are themselves suing UBS and Ernst & Young LLP, the fund’s auditor, seeking the return of the lost assets.

"We have battled with UBS regarding disclosure of information about the bank's knowledge of Madoff," Picard said.

"Unfortunately, they are still trying to shield this information from the public by designating all of their information as confidential. We intend to have the designation removed and the complaint made public as soon as possible."

A spokesman for the bank declined to comment.

Madoff's scheme could not succeed "unless UBS had agreed not only to look the other way, but also to pretend that they were truly ensuring the existence of assets and trades when in fact they were not and never did," said David Sheehan, counsel for the trustee.

Without UBS's serving as promoter, custodian and administrator, "Madoff's fraud would have been diminished in both scope and duration," Sheehan added.

At the time of his arrest, Madoff managed 4,900 accounts with $65 billion US in nonexistent investments. He is serving 150 years in federal prison for the fraud.

With files from The Associated Press