A British Columbia judge has certified a class-action lawsuit against Microsoft that alleges the software giant engaged in anti-competitive behaviour that enabled it to charge higher prices for its products.

Justice E.M. Meyers concluded in a ruling released Monday that Vancouver-based Pro-Sys Consultants, which is leading the plaintiffs in the case, has met requirements for certification for the lawsuit to proceed as a class action.

The legal action against Microsoft (NASDAQ:MSFT) was launched in 2006 on behalf of a number of indirect purchasers who acquired Microsoft software from resellers and from those who had Microsoft software pre-installed on their computers.

They argue they were forced to pay more for the software component of their purchase as a result of Microsoft's anti-competitive actions.

Pro-Sys alleges that the indirect sellers suffered harm from paying prices that were artificially inflated by anti-competitive behaviour.

Its statement of claim alleges wrongdoings dating back to the 1980s, when Microsoft emerged as the standard for operating systems "but by engaging in anti-competitive conduct Microsoft increased, maintained and abused its dominance in the market."

None of the claims have been proven in court.

Meyers narrowed the scope of the suit to cover British Columbians who indirectly acquired a licence for Microsoft operating systems or application software for their own use and those who bought computers with pre-installed Microsoft software since January 1994.

Microsoft said around 582 operating systems and 879 applications are at issue in the litigation.

Pro-Sys has referred to the case as one with a "dream record," because of a plethora of existing evidence from similar cases in the United States.

Twenty-three similar lawsuits have been launched against Microsoft in various U.S. courts. A number of these actions have been settled.

EU antitrust regulators in December dropped their last pending antitrust case against Microsoft after the company offered to let users choose between its browser and others. This ended more than a decade of legal trouble that resulted in euro1.7 billion in fines for Microsoft.