A federal agency is suing Walmart for discriminating against pregnant employees.

The US Equal Employment Opportunity Commission (EEOC) said on Friday that it had filed a class action lawsuit alleging that Walmart violated the law when it refused to accommodate pregnant employees' requests for a lighter work load.

According to the EEOC, Alyssa Gilliam and other pregnant employees at a Walmart warehouse in Menomonie, Wisconsin, were not allowed to take part in a company program that allowed some workers to receive lighter duties.

"Walmart deprived pregnant workers of the opportunity to participate in its light duty program. This amounted to pregnancy discrimination," said Julianne Bowman, the EEOC's district director in Chicago.

Pregnancy discrimination in employment is prohibited by the 1964 Civil Rights Act. The EEOC is seeking back pay, punitive damages, and "measures to correct Walmart's practices going forward."

Walmart denied the allegations.

In a statement, Walmart said that its accommodation policies have been updated several times in recent years to comply with or go further than state and federal laws, including the Americans with Disabilities Act and the Pregnancy Discrimination Act.

"Walmart is a great place for women to work," the company said. "We do not tolerate discrimination, and we support our associates by providing accommodations every day across all of our stores, clubs, distribution centers and offices. This case is not suitable for class treatment, and we deny the allegations."