Carphone Warehouse operates TalkTalk in several countries

Europe's biggest mobile retailer said TalkTalk customers would be able to call other TalkTalk users in Ireland or Britain free of charge.

Carphone's move into the Irish market pitches the company against Ireland's dominant telecoms operator, Eircom.

The retailer is aiming to sign up 2 million customers to its TalkTalk service in the UK by March 2008.

Carphone said customers joining TalkTalk in Ireland would not be charged a joining fee. The UK company plans to charge a monthly bill for line rentals and calls.

"I think people are paying far too much for telephone calls in Ireland and we recognised this as an opportunity to introduce a new cost-saving telephone service," said Carphone's chief in Ireland, Stephen Mackarel.

Carphone has been rapidly expanding its TalkTalk service and already has operations in France, Spain, Germany, Switzerland and Belgium.