In the latest and potentially most damaging salvo in an increasingly bitter family feud, the N.F.L. players union filed a complaint in federal court Wednesday charging the N.F.L. with collusion, saying team owners had a conspiracy to create a secret salary cap in the uncapped 2010 season.

The suit, filed in the United States District Court in Minneapolis, stems from the same issue that led the Washington Redskins and the Dallas Cowboys to be docked millions of dollars in salary-cap space in March.