Using a mobile phone abroad, known as roaming, is convenient but can be surprisingly expensive, according to Holiday Which? magazine.

If consumers decide to take their mobile phones abroad, they need to plan in advance to reduce bills. Costs can be reduced by arranging to divert calls to voicemail and accessing them on return from holiday; or by getting incoming calls barred completely, if this makes sense on a particular tariff; or by subscribing to an international call plan.

Prepay customers will usually pay much more to make and receive calls than those who pay monthly - a situation that Oftel is currently investigating.

For example, prepay users with Orange are charged double the monthly customers' rates to phone home or receive calls from the UK in Europe, making a five-minute call home from Europe cost £6 rather than £3.

Receiving calls in Europe as a monthly customer with Orange and Virgin is a pretty good deal at 30p per minute - around half the price of making calls back to the UK. At the other end of the scale, whether taking or making calls, prepay Vodafone users are stung a whacking £9.95 for a five-minute chat from the US.

Indeed, there are compelling cost arguments in favour of leaving the mobile at home with the cat when on holiday. Phonecards offer much cheaper rates - as low as around 7p a minute to call from France or 6 cents a minute from the US. But the convenience of using a mobile can be a hard habit to break.

Paying to receive calls

Patricia Yates, editor of Holiday Which?, said:

"The cost of that mobile phone "wish you were here" call home has caught out many holidaymakers.”

“Neither is it any use getting them to ring you instead as - unlike land-line phones - you can also pay a hefty bill to receive calls, send text messages, or access voicemail while abroad. And if you use your mobile to make a reservation at a local restaurant, you could pay even more than for an international call."

"If you fail to plan in advance, your tan may turn pale when the bill arrives!"