European Union Competition commissioner Neelie Kroes has slammed comments from the US Department of Justice about Monday's European court ruling on an antitrust judgment against Microsoft.

Kroes described the criticism of the ruling as "totally unacceptable" during a news conference in Brussels on Wednesday.

The DoJ's assistant attorney general for antitrust, Thomas Barnett, criticised the EC ruling sharply on Monday, warning that it could "have the unfortunate consequence of harming consumers by chilling innovation and discouraging competition."

Kroes fired back: "I think it is totally unacceptable that a representative of the US administration criticise an independent court of law outside its jurisdiction. It is absolutely not done. The European Commission does not pass judgement on rulings by US courts and we expect the same degree of respect from US authorities for rulings by EU courts."

On Monday the Court of First Instance, Europe's second-highest court, dismissed an appeal by Microsoft against the Commission's 2004 antitrust ruling against the company.

The DoJ statement added: "In the United States, anti-trust laws are enforced to protect consumers by protecting competition, not competitors." Barring "demonstrable consumer harm, all companies, including dominant firms, are encouraged to compete vigorously."

Kroes, who plans to visit Washington DC in the coming weeks, said that if Microsoft is unhappy with the court ruling it should appeal it to Europe's top court, the Court of Justice.