Luxembourg  - The European Union was right to put a cap on the charges mobile phone companies levy on customers who use their phones abroad, a top EU lawyer said Thursday.

The opinion comes as a blow to four of Europe's biggest mobile phone operators - Vodafone, Telefonica O2, Orange and T-Mobile - as they bid to scrap the EU's limit on roaming charges in a case presently before the European Court of Justice (ECJ).

According to the lawyer, the ECJ's Advocate General Miguel Poiares Maduro, the EU "was entitled to adopt the regulation" on roaming charges because of the high fees involved.

According to the European Commission, the EU's executive which drew up the regulation, mobile phone operators regularly made profits of up to 200 per cent on calls made abroad, and of up to 400 per cent on calls received by the customer while abroad.

Those charges "could reasonably be regarded as discouraging the use of cross-border services, such as roaming," Maduro said.

Since the commission is authorized to remove restrictions to cross-border trade in the EU, its regulation, which set a maximum price on calling and receiving calls, is in line with EU law, Maduro said.

ECJ cases regularly use the services of the advocates general, who act as legal experts and provide an independent opinion on the arguments presented in court.

Their opinions are not binding on the court as it makes its deliberations, but the Luxembourg-based body's judgements usually follow the lines argued in the opinions.

The court is expected to come out with its official verdict within the next few months. ECJ judges have already heard the arguments in the case, and are now conducting their deliberations. (dpa)