A ruling by the EU's top court on market dominance involving two US companies in Germany has strengthened the European Commission's case against the software giant Microsoft, an EU spokeswoman said yesterday.

The European Court of Justice earlier set out guidelines under which a firm - in a case involving the German units of NDCHealth Corp and IMS Health - could be said to be abusing a dominant position, the same charge levied by the EU executive against Microsoft.

"What the court has done is to set out the exceptional circumstances where refusal to grant a licence by a company which has a dominant position might be construed as an abuse," said Commission spokeswoman, Ms Amelia Torres.

"We believe that these exceptional circumstances, as set out by the court in the IMS case, have been met too in the Microsoft case," she said.

The case reviewed concerned the rights to a system of collecting drug sales data owned by IMS. The court said an abuse of a dominant position could come when a refusal to share data with a rival reserved the market in question to the bigger firm and eliminated competition.

Such abuse could also happen when a company refused to share data with a company that was going to offer a new product or service to the market.

Last month the Commission ordered a fine on Microsoft of almost €500 million after finding it abused a dominant position.