Wal-Mart Stores Inc. tried to head off worker protests at its stores over the Thanksgiving holiday by filing an unfair-labor-practice complaint against a union the company says is behind the protest plans.

The complaint, which Wal-Mart filed Thursday against the United Food and Commercial Workers International Union, asks the National Labor Relations Board to issue an injunction against worker rallies and pickets that have been staged at Wal-Mart stores and warehouses across the country for at least the last six months.

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