Carphone Warehouse has opened up a potential price war on overseas calls by launching its own international mobile phone service.

The phone specialist aims to win over customers from rival mobile networks or those who use calling cards to dial abroad - an industry said to be worth £500 million a year.

It claimed people could save up to 98 per cent on calls by using Mobile World.

The move follows the launch last month of Carphone's UK calling service Fresh. EasyJet founder Stelios Haji-Ioannou also entered the pre-pay telephone market a few weeks ago with no- frills service easyMobile. com. Mobile World, which is available from Carphone Warehouse outlets, is aimed at customers such as foreign workers and students who call home on a regular basis.

Rates include 5p a minute to landlines and mobiles in the United States, 6p to Australian landlines and 20p a minute to mobile phones in many countries. However, there is a

2.5p a minute surcharge on every call between 7pm and 9pm during the week.

The service also includes calls to UK landlines and mobile calls at 15p a minute at all times and texts for 7p. Both Fresh and Mobile World are virtual operators, meaning they use other providers' networks.

Foreign calls on Mobile World are cheaper because they are carried through Carphone's fixed-line operator Opal Telecom, while UK calls go through the T-Mobile network.

Customers use the service by buying a £9.99 SIM card for their own mobile phone. They then top up credit when they need it.

Research estimates that more than 50 providers sell some 150 million cards a year in the UK, and that about eight per cent of the adult population uses calling cards.