A proposed European Commission regulation on roaming mobile phone charges could cost operators 4.3 billion euros in lost sales and 2.3 billion euros in forgone profits, the GSM mobile phone operators' association, quoted by Dow Jones, said.
The trade group also said operators with the lowest domestic rates or operators that were only marginally profitable could see their profits fall by as much as 20%, according to the report.
The association, which represented more than 690 GSM mobile phone operators across 213 countries, made the calculations in its formal submission to the commission, the report said.
The report said European Information and Communication Commissioner Viviane Reding announced plans in April for a cut of up to 40% in the fees, which were added to calls dialed or received abroad.
The GSM Association said its members were voluntarily cutting roaming tariffs and this "downward trend" would "accelerate this year," according to the report.