A decision in the Microsoft-EU anti-trust case could be delayed by another six months after a decision to increase the number of deciding judges from a panel of five to a full Grand Chamber of 13.

Thomas Vinje, lawyer for the European Committee for Interoperable Systems, a group of five tech firms that is supporting the Commission in its anti-trust case, said that the change could delay the final ruling until the end of 2006. They had been hoping for a final ruling by mid-2006.

The panel-size increase was outlined in a letter sent by the president of the EU Court of First Instance, Bo Vesterdorf, to all concerned parties in the Microsoft case. Vesterdorf outlined plans to change the judge currently presiding over the case, French Judge Hubert Legal, and handle the judgment himself.

Vinje said: "This could delay proceedings. They had been moving more rapidly than usual for a normal Chamber. Whether the Grand Chamber can move as rapidly as Judge Legal is questionable."

He added that the delay caused by the change could effect any final ruling that goes against Microsoft. He pointed out, for example, that the Commission decided to postpone implementation of its remedy on licensing communications protocols for its workgroup server software until after the court rules. If a final ruling is delayed beyond mid-year 2006, it would have "serious implications for the market", Vinje warned.

Originally, the hearing for the case was expected to take place this October or November with the ruling in the second or third quarter next year.

The need to brief the new judges on the case's complicated issues will be behind the delay. Vesterdorf will not need time to learn the case. He was the judge who decided against Microsoft last year when they asked for certain measures imposed by the Commission to be suspended pending the court's judgment. Vesterdorf argued that Microsoft failed to prove there would be "irreparable harm" to the company if the measures were imposed. However, the court later threw out the Commission's decision.

Vesterdorf's decision to hand the case to the Grand Chamber follows anger at an article Legal published in French specialist newsletter Concurrences (Competition) on competition law in which he called clerks of the court "ayatollahs" who acted as though they had more power than the judges. Vesterdorf is reported to have been furious when he read the article.

None of the parties is expected to contest Vesterdorf's proposal to hand the case to the Grand Chamber.