Austrian banker Sonja Kohn was a criminal soul mate of Bernard Madoff for 23 years, running an international network of banks and funds to help perpetrate the biggest fraud in financial history, a court-appointed trustee for the Madoff firm said on Friday.

Irving Picard, the lawyer recovering money for the victims of Madoff's decades-long multibillion dollar fraud, sued Kohn and the bank she founded, Bank Medici, as well as Italy's UniCredit and its unit, Bank Austria, and 53 other defendants.

The complaint in U.S. Bankruptcy Court in New York said the litigation seeks to recover $19.6 billion in damages.

Separate lawyers representing Kohn and Bank Medici, now known as 2020 Medici, were not immediately available to comment.

In Sonja Kohn, Madoff found a criminal soul mate, whose greed and dishonest inventiveness equaled his own, Picard said in a statement.

The complaint dubbed Kohn's part The Medici Enterprise and a deliberately Byzantine structure, and said elements had been purposefully concealed from the trustee, United States and other law enforcement authorities.

We believe that even more information regarding the full scope of this criminal enterprise will be revealed, Picard said.

Separately on Friday, Picard announced that his team of lawyers at Baker & Hostetler LLP had reached settlements totaling $80 million with an undisclosed number of charities and nonprofit organizations that withdrew more than they deposited in Madoff's firm.

Overall, about $2.6 billion has been recovered. The trustee and his lawyers have sued individual investors, hedge funds and banks for amounts totaling about $51 billion. They said on Friday that the estimate of the total lost in the Ponzi scheme is approximately $19.6 billion.

Previous estimates of the amount of money that flowed through Bernard L. Madoff Investment Securities LLC (BLMIS) over the decades have varied from as much as $65 billion by U.S. prosecutors to $21.2 billion by the trustee.

Madoff, 72, is serving a 150-year prison sentence after pleading guilty in March 2009 to orchestrating a massive Ponzi scheme, one in which early investors were paid with the money of new clients and almost no actual trading took place.

Madoff maintained that he acted alone, but criminal charges have been filed in the United States against seven others, former employees and an outside accountant.

KOHN'S CENTRAL ROLE

The 161-page complaint claimed that $9.1 billion of stolen money was directly attributable to Kohn, her relatives and a labyrinth of feeder funds and banks in Austria, Italy and Gibraltar.

Timothy Pfeifer, counsel at Baker & Hostetler LLP, said that those accused in the Kohn lawsuit were arguably the single most critical building block for Madoff's massive fraud.

The amount sought by Picard in the Kohn lawsuit was the largest yet in his bid to collect Madoff money to repay thousands of swindled investors who have made claims in the same court.

It was also the first to cite racketeering claims.

The liquidator of BLMIS has filed a blizzard of lawsuits in recent weeks to meet a mid-December legal deadline, the second anniversary of Madoff's arrest.

The complaint against Kohn said that Madoff kept records of the BLMIS accounts for which he secretly paid Kohn and may have tried to destroy them before he was caught. Madoff secretly paid Kohn at least $62 million in secret kickbacks for bringing investors to BLMIS, the complaint said.

Kohn and the Medici Enterprise fed almost $4 billion through so-called feeder funds into BLMIS, including Primeo Fund, Thema International, Herald Fund, Alpha Prime Fund, Senator Fund, and Herald (Lux), the complaint said.

It said they had nominally different operating structures or regulatory regimes, but were functionally identical, as each was invested exclusively through BLMIS.

The case is Irving Picard v Sonja Kohn et al, U.S. Bankruptcy Court for the Southern District of New York, No. 10-5411.

(Additional reporting by Sylvia Westall, editing by Dave Zimmerman)