Vodafone will begin offering its 1.7 million Irish customers an all-Ireland tariff from early next year, the firm said yesterday.
The firm confirmed its decision shortly after the Minister for Communications, Mr Ahern, criticised mobile firms for charging users high "roaming tariffs".
These are the fees that mobile companies levy on customers when they make or receive calls while travelling abroad.
The tariffs vary considerably depending on the mobile phone network that users roam on when abroad, but are often up to 20 or 30 times more expensive than calls made on a home network.
In an address to the Commission for Communications Regulation (ComReg) annual conference yesterday, Mr Ahern said the public, North and South, were paying through the nose for mobile phone services when they travelled over the Border to Northern Ireland and vice versa.
He called on all the mobile firms to abolish the fees.
Vodafone confirmed it would introduce an all-Ireland service early next year. This would enable its customers to make and receive calls while in Northern Ireland for the same price as calls made while in the Republic.
The new all-Ireland tariff will only apply when Vodafone Ireland customers are roaming on its sister company's network in Northern Ireland, Vodafone UK.
O2 Ireland already offers its customers the option of signing up for an all-Ireland tariff on a subscription basis, which costs users an extra €7.50 per month.
Once again, this all-Ireland service is only available to subscribers who chose to roam on O2 Ireland's sister firm while travelling in Northern Ireland, O2 UK.
Meteor, the State's third mobile phone firm, will not be able to abolish roaming charges for customers who travel to Northern Ireland.
The company, which is majority owned by the US mobile firm Western Wireless does not have a subsidiary company based in Britain.
Meanwhile, Ms Etain Doyle, chairman of ComReg, said it was currently undertaking a major study on roaming charges levied by Irish operators. She said the results of the study should be known soon.
Ryanair Telecom, a start-up telecoms firm claiming to offer users a discount of up to 25 per cent on call charges, launched this week in the Republic.
The firm is already offering some British consumers services for both mobile and fixed line telecoms. But in the Republic it will offer only fixed line services.
