Wal-Mart (WMT -0.19%) and the two staffing agencies it uses in the Chicago area were hit with a class action lawsuit alleging they broke federal minimum wage and overtime laws, according to a press release by the United Food and Commercial Workers International Union.

The suit, filed in U.S. District Court, Northern district of Illinois, Eastern Division, claims Wal-Mart and the staffing agencies required temporary employees to work extra hours without compensation.

The primary plaintiff in the lawsuit, Twanda Burk, said, "I only get paid minimum wage and yet Labor Ready [one of the staffing agencies] and Wal-Mart still try to cheat me by not paying me for the time I actually work." The other agency named in the suit is QPS.

The violations, according to the suit, began in early 2009 and have continued to the present time. The plaintiffs seek all unpaid wages and an injunction against Wal-Mart and the agencies to prevent future violations of labor laws.