Louisiana School Employees Retirement System and the Louisiana Municipal Police Employees Retirement System, both of Baton Rouge, have filed a class action lawsuit against Warner-Lambert Co., Morris Plains, N.J. The complaint, filed in the Delaware Court of Chancery, seeks to prevent the companys board of directors from allegedly breaching fiduciary duties to its shareholders by merging with American Home Products Corp., Madison, N.J. The funds allege the breach occurred when Warner-Lambert agreed to merge with American Home without giving due consideration to a competing bid by Pfizer Inc., New York. The $1.4 billion School Employees fund and the $1 billion Municipal Police fund each will seek the lead plaintiff role in the case, said Daniel Berger of Bernstein Litowitz Berger & Grossman, the funds attorney. The pension funds collectively hold more than $10 million in Warner-Lambert common stock.