Whole Foods Market Inc. launched a rare corporate counterattack on a federal agency, appealing to Congress and filing a lawsuit to stop a continuing Federal Trade Commission challenge to a merger that closed a year ago.

The lawsuit, filed Monday in U.S. District Court in Washington, alleges prejudice and due-process violations against Whole Foods by the FTC, which challenged the grocer's $565 million buyout of Wild Oats Markets Inc. The agency initially lost before the federal court, and the companies merged in August 2007.

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