The war of words between Microsoft and the European Commission over the software group's new flagship product has escalated, with Neelie Kroes, EU competition commissioner, denouncing what she called "a co-ordinated campaign" to discredit the regulator.

Ms Kroes, in a letter to the Financial Times, insists that the Commission is not conducting a "vendetta" against Microsoft. Brussels, she says, is simply trying to ensure that Vista, the operating system set to replace Microsoft Windows next year, complies with EU competition rules.