The Commission told Vodafone, Orange, T-Mobile and O2 yesterday that the high costs of data services, which allow people to access the internet and download music and e-mails on their handsets and PCs abroad, have "not escaped its attention".

Its comments came after research reported in The Times this week showing that some mobile companies charge up to 25 times the amount they charge in the UK for mobile data services abroad. A Commission spokesman told The Times: "We are keeping an eye on the situation, and if we find evidence of collusion or anti-competitive practices, then we will investigate."

Consumer groups are also increasing the pressure on mobile companies to take action on the "astronomical costs" for the services. A spokesman for the National Consumer Council said: "We are surprised that while Ofcom [the UK telecoms watchdog] is scrutinising charges for voice calls and text messages, it is not doing the same for data downloads. These could well be the next big thing for mobile users and must not be ignored."

Internet access has come to be a standard feature on mobiles. Users can access the net on 2.5G phones using so-called GPRS technology or on a "next-generation" 3G mobile or data card. Mobile operators regard data services as a key way of boosting their sales and helping them to claw back the cost of the £22.5 billion 3G licences.

Mobile companies have come under pressure from Brussels to bring down the cost of calls abroad, but consumer groups believe that they are exploiting the relatively new introduction of data services to crank up charges before people wake up to the costs.

Orange, for example, charges £1 to £3 a megabyte for data services in the UK. But Britons abroad will be charged up to £25 a megabyte. That means that downloading only one song or two chunky e-mail attachments while abroad could cost £100. Vodafone, the world’s biggest operator, charges £2.35 a megabyte at home for data services, but Britons abroad have to pay up to £10.28 a megabyte.

Customers have also complained about an alleged lack of transparency about pricing. Roger Steare, a consultant from Sevenoaks, Kent, came back from a business trip to face a huge data bill from Orange. "I have a special bundle in the UK where I pay £45 a month for 400 megabytes. When I went to France and Germany in September, I was billed £655.70 for 81.96 megabytes. I didn’t check the website because I trusted any premium would be reasonable, but I don’t think paying nearly 100 times what I am paying in the UK is fair and reasonable."

The high data costs are in addition to mark-ups on regular calls and texts. Calls can cost up to £1.50 a minute to Britain from Europe.

The operators claim that the high costs reflect their own costs to provide the service. To allow customers to download data abroad, they say, they have to put in place costly wholesale agreements with other mobile operators and landline operators. They must also cover, they say, the cost of setting up and managing the partnerships.

A spokesman for Orange said: "We are reviewing our pricing to ensure that customers who download data while abroad are receiving the best value."

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