The Justice Department has called on the Securities and Exchange Commission and the U.S. Commodity Futures Trading Commission to make some of their rules dealing with over-the-counter derivatives more stringent, arguing that the rules don’t go far enough to keep groups of major market players from banding together to control derivatives exchanges.

In separate comment papers sent to each agency today, Christine Varney, who heads the Justice Department’s Antitrust Division, says that DOJ supports the rules proposed by the SEC and the CFTC to limit to 20% the amount that individual derivatives dealers can own of security-based swap execution facilities and national securities exchanges.