A new lawsuit accused Wal-Mart Stores Inc (WMT) and two staffing agencies of requiring temporary employees to show up early for work, stay late, and work through lunch at the world's largest retailer.

The proposed class action, filed on Monday in a Chicago federal court, alleged Wal-Mart and the agencies violated minimum wage and overtime laws which could affect several hundred temporary workers in the Chicagoland area.

Wal-Mart declined to comment immediately, saying it first needed to review the lawsuit.

Wal-Mart has faced protests in various U.S. cities lately and some workers have planned to walk off the job on Black Friday, the busy shopping day right after Thanksgiving. Such actions are being sponsored by a groups including a contingent of workers called OUR Walmart that is trying to speak out about what it says are tough working conditions.

In early October, workers who are part of OUR Walmart staged what the group called the first-ever strike against Walmart in Los Angeles, while Walmart itself called the event in Los Angeles a rally. Walmart store employees also walked off the job in other cities including Dallas in actions sponsored by OUR Walmart.

Longer strikes also took place at a Southern California warehouse and at a distribution center in Illinois that supplies Walmart stores.

OUR Walmart, a group of current and former Walmart employees, is backed by the United Food & Commercial Workers International Union. UFCW members work at grocery stores that compete with Walmart.

Wal-Mart has said that OUR Walmart represents just a small fraction of its 1.4 million U.S. employees.

Wal-Mart's labor practices have garnered criticism among consumers and have gotten attention in the press, but so far have not affected investors. Roughly half of Wal-Mart's stock is controlled by descendents of company founder Sam Walton.

In 2008 Wal-Mart agreed to pay as much as $640 million to settle dozens of federal and state class-action lawsuits alleging it deprived workers of wages. In separate litigation last year, the U.S. Supreme Court ruled that women suing Wal-Mart for gender discrimination could not proceed as a national class action.

The latest lawsuit in Chicago says Wal-Mart also failed to pay temporary workers a minimum of four hours' pay on days a laborer was contracted to work, but was not utilized for a minimum of four hours.

The case in U.S. District Court, Northern District of Illinois is Twanda Burkes et al, on behalf of themselves and all other persons similarly situated, vs. Wal-Mart Stores Inc., Labor Ready Midwest Inc. And QPS Employment Group Inc., 12-08457.