Mobile phone operators in Europe could be forced by the European Union to cut the expensive fees customers pay for calling while abroad.
Greater transparency has failed to reduce roaming charges
The European Commissioner for Information, Society & Media, Viviane Reding, will outline her plan at a meeting with national regulators today.
Speaking on BBC Radio 4 she said travellers were being penalised by "fantasy costs" for roaming.
She plans to cap overseas roaming costs at the level of a cross-network call.
The new law she is proposing will have to be passed by the European Parliament, and would probably not come into effect until 2007 or 2008.
The European Commission first scrutinised roaming charges as far back as 2000.
Since then the EC has staged several other investigations, and it has accused mobile phone companies in Germany and the UK of charging excessive wholesale tariffs to other operators.
Ms Reding said that although the wholesale cost of roaming - the charges that operators make to each other - have been coming down, the costs to individual phone users have not.
She made it clear that she had become fed up with the operators' inaction.
"I am proposing to act because I have left it to the market until now to get things right," she said.
"I have told the market in 2004 and 2005 that it had to bring the prices down. It didn't, so now legislative initiative is necessary to have these very frustrating prices, for the consumer, brought to normal."
That meant international roaming should not cost any more than making a domestic call to someone on another mobile network, she said.
Last October, the EC set up a website enabling people to compare roaming charges throughout the 25 member states of the European Union.
At the time the Commission said the cost of using a mobile abroad "is hard to believe" and hoped that greater transparency would lead to lower charges.