Walmart looks to block sex-biasclass action

Walmart received a boost this week when the US Supreme Court said it would hear the supermarket giant's attempt to block a massive sex discrimination class action lawsuit against it.

The claim, which is the largest sex-bias lawsuit in US corporate history, dates back to 2001. It was first filed by seven women, some of whom still work at Walmart, but it now covers up to 1.5 million former and current female employees.

The plaintiffs allege the practices of promoting men over women and paying them less for the same role across its 3,400 stores over the past decade were part of a common culture at Walmart. The retailer, which owns Asda in the UK, had appealed to the country's highest court in the summer over the lawsuit after a Californian appeals court gave it the green light in April.

The Supreme Court judges will not rule on whether Walmart is guilty of sex bias, but will decide if the grocer must defend itself against a single lawsuit that covers such a huge number of employees. If the case proceeds, it could cost Walmart $1bn or more in damages.

The case is being nervously watched by other large US corporations. Companies including the chip-maker Intel and the software giant Microsoft have reportedly supported Walmart's appeal.

The Walmart Stores Inc v Dukes case is named after Betty Dukes, the lead plaintiff, who is a store greeter for Walmart.

Prosecuting lawyers allege that the case is "large because Walmart is the nation's largest employer and manages its operations and employment practices in a highly uniform and centralised manner". But Walmart argues that this is unfair, saying that claims should focus more on locations or on an individual basis. Walmart said: "The current confusion in class action law is harmful for everyone – employers, employees, businesses of all types and sizes, and the civil justice system.

"These are exceedingly important issues that reach far beyond this particular case. We look forward to the court's consideration of the appeal."