BAKERSFIELD, Calif. -- Seeking to recover more than $200 million in illegal overcharges and penalties, Attorney General Edmund G. Brown Jr. announced Tuesday, that he has filed suit against State Street Bank and Trust -- one of the world's leading providers of financial services to institutional investors -- for committing "unconscionable fraud" against California's two largest pension funds -- CalPERS and CalSTRS.

The suit, which was unsealed Tuesday by a Sacramento Superior Court judge, contends that Boston-based State Street illegally overcharged CalPERS and CalSTRS for the costs of executing foreign currency trades since 2001.

"Over a period of eight years, State Street bankers committed unconscionable fraud by misappropriating millions of dollars that rightfully belonged to California's public pension funds," Brown said. "This is just the latest example of how clever financial traders violate laws and rip off the public trust."

The case was originally filed under seal by whistleblowers - "Associates Against FX Insider Trading," who alleged that State Street added a secret and substantial mark-up to the price of interbank foreign currency trades. The interbank rate is the price at which major banks buy and sell foreign currency.

Subsequently, Brown launched an independent investigation into the allegations.

Brown's investigation revealed that State Street was indeed overcharging the two funds. Despite being contractually obligated to charge the interbank rate at the precise time of the trade, State Street consistently charged at or near the highest rate of the day, even if the interbank rate was lower at the time of trade.

Additionally, State Street concealed the fraud by deliberately failing to include time stamp data in its reports, so that the pension funds could not determine the true execution costs by verifying when State Street actually executed the trades. Commenting on this deception, one State Street senior vice president said to another executive that "…if providing execution costs will give [CalPERS] any insight into how much we make off of FX transactions, I will be shocked if [State Street] or anyone would agree to reveal the information."

Brown's office estimates that the pension funds were overcharged by more than $56.6 million over eight years. The lawsuit asks for relief in the amount of triple California's damages, civil penalties of $10,000 for each false claim; and recovery of costs, attorneys' fees and expenses. It is estimated that damages and penalties could exceed more than $200 million.

Under California's False Claims Act, anyone who has previously undisclosed information about a fraud, overcharge, or other false claim against the state, can file a sealed lawsuit on behalf of California to recover the losses. They must notify the Attorney General as well.

Such a case is called a "qui tam" case. If there is a monetary recovery, the law provides that the whistleblower "qui tam plaintiff" receives a share of the amount recovered if the requirements of the statute are met.