A securities fraud lawsuit filed against Omnicom Group, a marketing and corporate communications company that pursued a “method of expansion by acquisition” of smaller agencies, can proceed as a class action, a federal judge has ruled.

Southern District of New York Judge John F. Keenan certified the class action in In re Omnicom Group Securities Litigation, 02 Civ. 4483, on behalf of potentially thousands of “persons and entities who purchased or otherwise acquired the securities of Omnicom from Feb. 20, 2001 through and including June 11, 2002.”