A regulator investigating the collapse of Jon Corzine’s securities firm, MF Global, said Thursday that the firm’s failure to separate its clients’ money from its own assets violated “the core foundation” of investor protection. Gary Gensler, chairman of the Commodity Futures Trading Commission, told a Senate panel Thursday that “the most troubling aspect about the MF Global situation is the shortfall of customer money at the firm.”

MF Global admitted to regulators early Monday that it had diverted hundreds of millions in client money. The company filed for bankruptcy protection Monday. The CFTC and the FBI are investigating whether it broke government rules or criminal laws.