A Mayer Brown partner was indicted Tuesday on charges he helped Refco Inc. conceal from investors that a company owned by former CEO Phillip R. Bennett owed Refco hundreds of millions of dollars.

Joseph P. Collins, head of the law firm’s derivatives group, was charged in the Southern District of New York with securities fraud and a host of other counts in connection with the 2004 sale of a majority stake in the financial services company and a 2005 initial public offering.