A US non-profit antitrust organization plans to file a lawsuit against Microsoft and the Department of Justice (DoJ), alleging that the parties did not fully disclose communication related to the proposed settlement of the government's case against the software maker.

The lawsuit will be filed by the American Antitrust Institute (AAI). It alleges that Microsoft and the DoJ failed to reveal all the information required under the Tunney Act, AAI president Bert Foer confirmed yesterday.

The Tunney Act sets procedures that must be followed whenever the US decides to settle a civil antitrust suit.

Although the DOJ and nine US states agreed to a proposed settlement in the government's antitrust case against Microsoft late last year, that settlement has come under heavy criticism by groups claiming that it does not do enough to clip the software maker's wings.

Another nine states, which had previously been part of the government's antitrust case, have declined to participate in the proposed settlement.

The nine dissenting states are lobbying for stiffer penalties against Microsoft for using its dominance in the PC operating systems market to impose unfair pricing policies. AAI is backing the nine states that have refused to settle with the DOJ.