The conflict between software giant Microsoft and the European Commission (EC) is likely to become more heated. According to a report from Financial Times, Microsoft has sent a 'strongly-worded' letter to the EC, in which it accuses the regulator of violating the software company's rights in the enforcement of its antitrust rulings.

The EC issued a Statement of Objections in December which threatened Microsoft daily fines of up to €2m if it did not comply with the EC's March 2004 antitrust ruling. In response, Microsoft first stated that it had submitted appropriate technical documentation to the EC, but that the regulator had not yet fully reviewed it. The company also said that the EC confused the difference between revealing Windows source code, which Microsoft was willing to do to allow companies to provide interoperable applications, and Windows internals, which it was not willing to do, as it would allow competitors to make Windows clones.

In a surprise move last week, before it had issued an official response to the EC's Statement of Objections, Microsoft announced that it would license its Windows source code in Europe. In this new letter, though, Microsoft reportedly claims that it has not been given access to the documentation which form the basis of the EC's allegations and therefore cannot sufficiently defend itself. Specifically, the company claims that it has been given access to 29 out of 100 documents, and that 25 of those consisted of Microsoft-EC correspondence.

In the letter, Microsoft claims that the EC has violated its rights of defence. An EC spokesperson said that Microsoft's claims are premature, as the EC has made no official decision nor imposed any fines on the software maker.