A coalition of technology giants has mounted a legal challenge to Microsoft’s dominance of the software market in Europe in a move that could reignite the brutal “browser wars” of the 1990s.

The action comes three months after the world’s largest software developer was forced to pay a fine of €497 million (£356 million) when it suffered a comprehensive defeat at the hands of the European Union’s competition authorities in a similar case.

Opera, a small Norwegian company that makes a web browser competing with Microsoft’s market-leading Internet Explorer (IE), yesterday filed a complaint with the European Commission. It alleges that Microsoft’s practice of building IE into its Windows operating system, used on 90 per cent of computers, illegally handicaps rival browsers. Opera also claims that the US group’s decision not to follow open industry standards impedes smaller rivals.

The attack on Microsoft is being backed by the European Committee for Interoperable Systems (ECIS), of which IBM, Oracle, Nokia and Sun Microsystems are members.

Thomas Vinje, ECIS’s counsel, said: “Microsoft deprives consumers of real choice in internet browsers. Browsers are the gateway to the internet. Microsoft seeks to control this gateway.”

Microsoft, which has said that it is out “to win the internet”, denied that it stifles competition. A spokesman said: “It’s important to note that computer users have complete freedom of choice to use and set as default any browser they wish, including Opera, and PC manufacturers can also preinstall any browser as the default on any Windows machine they sell.”

He added that IE “has been an integral part of the Windows operating system” for more than a decade.

Microsoft said that it is ready to cooperate with the latest proceedings, but it will be deeply unenthused by the prospect of returning to Brussels to defend yet another competition case. In September, the company suffered a bruising blow from European judges who upheld a record €497 million fine. The penalty was imposed on Microsoft for abusing its dominant market position by bundling its Media Player software, used to access video and audio content online, into Windows.

The European Court of First Instance also upheld a Commission order that Microsoft supply technical information to other companies so they can make products compatible with Windows-based software.

The ECIS suggests that the Opera complaint parallels that on Media Player bundling. The latest legal action also echoes a case brought in America in 1998, in which the US Justice Department won a ruling against Microsoft for competing illegally with Netscape, a former market-leading browser that was crushed when Microsoft effectively began giving IE away, That ruling nearly led to Microsoft being broken up before it agreed a settlement in which it agreed to help its rivals to build products that run on Windows.

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