Browser firm Opera Software yesterday filed an antitrust complaint against Microsoft with the European Commission.

The complaint alleges Microsoft is abusing its dominant position by tying its browser, Internet Explorer, to the Windows operating system and by "hindering interoperability by not following accepted web standards".

Opera said it is requesting that the Commission to take the necessary actions to compel Microsoft to give consumers "a real choice and to support open web standards" in Internet Explorer.

"We are filing this complaint on behalf of all consumers who are tired of having a monopolist make choices for them," said Jon von Tetzchner, CEO of Opera.

"In addition to promoting the free choice of individual consumers, we are a champion of open web standards and cross-platform innovation. We cannot rest until we've brought fair and equitable options to consumers worldwide."

Opera requests the Commission to implement two "remedies to Microsoft's abusive actions". First, it requests the Commission to obligate Microsoft to unbundle Internet Explorer from Windows and/or carry alternative browsers preinstalled on the desktop.

Second, it asks the European Commission to require Microsoft to follow fundamental and open web standards accepted by the web-authoring communities. " The complaint calls on Microsoft to adhere to its own public pronouncements to support these standards, instead of stifling them with its notorious 'Embrace, Extend and Extinguish' strategy. Microsoft's unilateral control over standards in some markets creates a de facto standard that is more costly to support, harder to maintain, and technologically inferior and that can even expose users to security risks," Opera stated.

"Our complaint is necessary to get Microsoft to amend its practices," added Jason Hoida, deputy general counsel, Opera.

"The European Court of First Instance confirmed in September that Microsoft has illegally tied Windows Media Player to Windows. We are simply asking the Commission to apply these same, clear principles to the Internet Explorer tie, a tie that has even more profound effects on consumers and innovation. We are confident that the Commission understands the significance of the Internet Explorer tie and will take the necessary actions to restore competition and consumer choice in the browser market."