Norwegian-based web browser company Opera has submitted an antitrust complaint to the European Commission about Microsoft.

The complaint is the first since the software giant lost its landmark European antitrust case in September.

Opera claims Microsoft illegally ties the Internet Explorer web browser to its Windows operating system, and that consumers are less likely to use Opera's alternative software as a result.

The claim is backed by an industry group, the European Committee for Interoperable Systems (ECIS), which includes IBM, Oracle and Nokia.

"By tying Internet Explorer to its monopoly operating system and refusing to faithfully implement industry accepted open standards, Microsoft deprives consumers of a real choice ," says the ECIS statement.

Two months ago Microsoft lost its appeal against a record €497 (£343m) ruling by the European Commission that the bundling of its Media Player software is anti-competitive. The ruling said that the vendor must share information with rival software companies to ensure products can be made compatible.

But Opera's claims regarding browsers are undermined by the widespread use of the Mozilla Firefox browser , according to Jonathan Zuck, president of the Association for Competitive Technology, which represents more than 3000 software vendors.

"After four years of no growth, Opera is looking for someone to blame for its failures and Microsoft is always an easy target," said Zuck.

"With the Firefox web browser grabbing as much as 20 per cent of the market in some European countries, it is clear that companies can compete and beat Microsoft in the browser market.”