US supermarket titan Wal-Mart is struggling to fend off a huge sexual discrimination lawsuit, which could turn into the biggest civil-rights court case in history.
Wal-Mart has always insisted its staff are happy
A US judge is currently pondering an application to bundle together claims from up to 1.6 million present and former Wal-Mart employees, who say women were routinely underpaid and overlooked for promotion.
Lawyers want to upgrade the initial lawsuit - launched by six women working for Wal-Mart in California - into a class action, meaning all equivalent cases will be treated in one blanket judgement.
Wal-Mart argues that variations in pay and conditions are an inevitable part of its staff structure, and wants to make sure discrimination complaints are handled on a store-by-store basis.
One size fits all
Lawyers for the plaintiffs say that a class-action case makes sense, since Wal-Mart's 3,500 US stores are more or less identical.
The company fosters a strong common culture - a culture, the complaints say, of routine discrimination against female staff.
"Women have been paid less than men at Wal-Mart every year since 1976, in every managerial position," Brad Seligman, a lawyer for the workers, told the judge.
"Every store is closely supervised and every store is connected in a real-time way, and all management are trained together.
"This is not a case involving disparate autonomous stores."
Wal-Mart is keen to avoid a high-profile case, since it has made much marketing capital from the happiness of its 962,000 US staff.
The firm argued that any variations in pay were accounted for by differing job specifications.
Not all jobs demand the same skills, Wal-Mart says
On the shop floor, workers with special qualifications - gun licences, for example, or animal-handling skills - are paid more to work in specialised parts of the store.
It has also pointed out that a class-action case would become unwieldy.
One lawyer for the firm said it would seek testimony from 4,000 store managers in a class-action case, resulting in a trial that would last 13 years.
If class-action status is approved, the case will certainly be the biggest of its kind in legal history.
US companies face a mounting wave of such litigation, most frequently in complaints arising from shareholders and consumers - notably a series of class-action suits launched against tobacco firms by smokers.
In some cases, they generate damages claims rising into the billions of dollars, but so far few of the very large class actions have achieved the desired results.
For plaintiffs, class actions represent a convenient way to bring a case to court with legal representation that they could not ordinarily afford.