Wal-Mart Stores Inc. asked a federal appeals court on Tuesday to review a judge’s decision last month that a sex-discrimination lawsuit against the retailing giant could proceed as a class-action.

The Wal-Mart appeal comes after U.S. District Judge Martin Jenkins in San Francisco certified the class of some 1.6 million women who worked for Wal-Mart’s U.S. stores since Dec. 26, 1998.

The lawsuit, filed in 2001 and which marks the largest civil rights class-action case in U.S. history, accuses the company of discriminating against women employees and retaliating against those who complained.

Wal-Mart, the world’s largest retailer, has denied discrimination and argued the number of men in management reflected the higher number of men who apply for those jobs.

“This court should review this unprecedented, unmanageable, and unconstitutional class now, before the parties and the district court are forced to devote vast amounts of time and resources litigating an action that would not in the end survive judicial review,” the 29-page petition to appeal said.

The Bentonville, Arkansas-based company faces dozens of lawsuits claiming violations of wage-and-hour laws and discrimination, but analysts think this one in particular could prove costly.

For example, Home Depot Inc. (HD.N: Quote, Profile, Research) settled a sex discrimination case in 1997 for $104 million in a case that covered just 25,000 women.