Wal-Mart Stores Inc. lost its appeal to reverse the granting of class action status to a group of about 2 million female workers with sex-bias claims–considered the largest sexual discrimination case in U.S. history.

A three-judge panel of a federal appeals court in San Francisco again rejected the nation’s biggest private employer’s request to throw out a 2004 lower court ruling granting class action status to the lawsuit. The court found the judge did not err in granting class certification. In February the panel had ruled similarly, upholding the lower court.

The lawsuit was originally filed in 2001 by six women to include all women who worked at Wal-Mart stores from December 1998 to the present, excluding upper management and pharmacy employees. The women accuse Bentonville, Ark.-based Wal-Mart of paying women less than men and giving them fewer promotions.

Wal-Mart will now appeal the 2004 decision with a full nine-judge panel and will have to restart its request for the rehearing.