By David Kravets The Associated Press

SAN FRANCISCO – A federal appeals court ruled yesterday that Wal-Mart Stores Inc., the world’s largest private employer, must face a class-action lawsuit alleging as many as 1.5 million former and current female employees were discriminated against in pay and promotions.

The ruling by the 9th U.S. Circuit Court of Appeals upholds a 2004 federal judge’s decision to let the nation’s largest class-action employment discrimination lawsuit go to trial, possibly exposing the Bentonville, Ark.-based retailing powerhouse to billions of dollars in damages.

“Plaintiff’s expert opinions, factual evidence, statistical evidence and anecdotal evidence present significant proof of a corporate policy of discrimination and support plaintiff’s contention that female employees nationwide were subjected to a common pattern and practice of discrimination,” the court wrote in a 2-1 decision.

Wal-Mart said it would ask the court to rehear the case with the same three-judge panel or with 15 judges, a move likely to idle the case for months. Yesterday’s ruling came 18 months after the case was argued.

“This is one step of what is going to be a long process,” Wal-Mart attorney Theodore Boutrous Jr. said. “We are very optimistic of obtaining relief from this ruling.”

He said Wal-Mart’s own review found no significant disparity in pay between men and women at 90 percent of its stores.

Wal-Mart, which employs 1.3 million workers, claimed the conventional rules of class action suits should not apply in the case because its 3,400 stores, including Sam’s Club warehouse outlets, operate like independent businesses, and the company didn’t have a policy of discriminating against women.