Britain's communications regulator Ofcom said it was investigating whether consumers are overcharged for using their mobile phones abroad.
Charges for "international roaming," a service allowing mobile phone users to make and receive calls and text messages while travelling abroad, have become the bane of holidaymakers and business travellers, with some operators imposing hefty and sometimes complex charges to connect via overseas networks.
A spokesman said Ofcom was looking at two issues. "One thing is that people are unsure of charges they are going to incur when they travel abroad."
"The second issue is to look at the international market and at the amount one operator charges another. The European Commission is working with national regulators on an initiative to combat unfair behaviour by networks," he added.
Ofcom said it could act, along with other European regulators, if the EC found network operators were acting unfairly.
Ofcom voiced concern over international roaming last year but has stated that it currently has no plans to introduce regulation into the relatively young market.
The European Commission's competition division is already pursuing mobile operators Vodafone and O2 in Britain and T-Mobile in Germany over concerns that retail and wholesale roaming prices are excessive.