Microsoft's appeal against the European Union's antitrust ruling will be judged by Bo Vesterdorf, the president of the Court of First Instance (CFI).

Vesterdorf was the judge who in December 2004 threw out Microsoft's attempt to temporarily halt measures imposed by the European Commission, the EU's antitrust watchdog, in April last year.

A court official said a decision was taken on Thursday to have the case heard by a Grand Chamber of 13 judges, presided over by Vesterdorf, rather than by a five-judge team led by Hubert Legal.

Though the court official would not comment on reasons for the change, it is understood to reflect anger at an article by Legal in which he attacked clerks at the court as "ayatollahs of the free market." There had been speculation that Legal, a French national, would stay on as "judge-rapporteur" (reporting judge), but the court has decided to appoint Irish judge John Cooke to this position.

The case is now likely to stretch until late 2006.