A judge in the US has given the green light for a gender discrimination lawsuit against Wal-Mart to become a class action. This could involve up to 1.6 million present and former employees at the world's leading retailer.

Lawyers involved in the case claim that there is systemic discrimination against women, alleging that they claim, on average, US$1400 less per year than their male counterparts doing the same job.

The lawsuit may now become a class action, the judge has determined, making it the biggest civil rights case against a private US company ever. The case stems from a lawsuit filed three years ago by six women who were either employed by Wal-Mart or were former employees (or 'associated', as the company terms its staff).

The allegations extend beyond lower pay for the same work to include preferring men over women when promotions are under consideration.

Wal-Mart had submitted the argument that a class action lawsuit would be too unwieldy, but the San Francisco judge Martin Jenkins dismissed this argument.

"This ruling brings Wal-Mart one giant step closer to being as vigilant in accounting for equal pay and promotional opportunities for women as it is in keeping track of its stock of toothpaste, tires and t-shirts," said plaintiffs' co-counsel Irma D. Herrera, executive director of San Francisco-based Equal Rights Advocates.

In an official comment on the ruling, Wal-Mart chief spokesperson Mona Williams said: "Let's keep in mind that today's ruling has absolutely nothing to do with the merits of the case. Judge Jenkins is simply saying he thinks it meets the legal requirements necessary to move forward as a class action. We strongly disagree with his decision and will seek an appeal."