The move, announced yesterday, could lead to regulators taking action to reduce prices, such as imposing controls on wholesale roaming rates.
The European Regulators Group said that all 25 national telecoms authorities in the EU were sending a questionnaire to mobile operators to ask for key data to help them judge whether additional regulation was necessary to ensure competition in the market. The group hopes to draw conclusions from the evidence it receives by May 2005.
EU IT commissioner Viviane Reding said this week that roaming charges were "outrageously high" and that "urgent action" was needed to tackle them.
The move by the European Regulators Group follows an investigation by the EU into roaming rates charged by UK mobile operators O2 and Vodafone. The European Commission told the two that their charges were too high and detrimental to users. The commission is waiting to receive a response from O2 and Vodafone before deciding what action to take.