(CN) - The U.S. National Labor Relations Board charged Wal-Mart for disciplining and sometimes firing employees who protested their wages and working conditions.
More than 60 Wal-Mart supervisors and one corporate officer are named in the complaint.
Between May 29, 2013, and June 8, 2013, Wal-Mart employees in 13 states went on strike in the first prolonged strikes in the retail giant's history.
The complaint claims that Wal-Mart Vice President David Tovar went on national television twice in 2012 and "threatened employees with unspecified reprisals if they engaged in concerted activities and/or engaged in activities for mutual aid and protection."
Leading up to the strike, the company also required store managers to read a corporate memorandum to its employees that said in part: "Should you participate in further union-orchestrated intermittent work stoppages that are part of a common plan or design to disrupt and confuse the company's business operations, you should expect that the company will treat any such absence as it would any other unexcused absence... [T]he company does not believe that these union-orchestrated hit-and-run work stoppages are protected activity."
Wal-Mart implemented a policy in May 2013 that treats absences for striking workers as unexcused absences.
Workers around the country who participated in the strike received disciplinary notices for their absence, or were fired.
The action names more than 60 employees who received some form of discipline, including 19 who were fired, allegedly as a result of their protected right to organize.
Though the NLRB said its preliminary investigation found that the employees' charges against Wal-Mart likely had merit, the agency could not settle with the retailer.
Under the National Labor Relations Act, private sector employees are guaranteed the right to organize to improve their wages and working conditions, with or without a union.
Wal-Mart spokeswoman Brooke Buchanan defended the company in an interview with the Chicago Tribune.
"We believe that our actions were valid," she said. "We take our obligations very seriously. We look forward to sharing our side of the facts in these cases with a judge."
Wal-Mart has until Jan. 28 to respond to Wednesday's filing.
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