BT has launched a new mobile application called SmartTalk that allows customers of its home phone calling plan to transfer their inclusive minutes over to their iPhone or Android smartphone.

According to BT, the app works best over wi-fi, but will also work over any mobile data connection. Customers who make phone calls via the app on their smartphone are billed as if they were calling from their BT landline.

This means they can not only make inclusive calls to UK landlines, 0800, 0845 and 0870 numbers, they can also phone home for the price of a UK call when travelling abroad.

“This is a really exciting breakthrough that means you can take your BT calling plan with you and continue saving money when you’re away from home,” said John Petter, managing director consumer at BT.

“At last you can actually call freephone 0800 numbers for free from mobiles and get inclusive 0845 and 0870 calls too. And of course, you can take advantage of BT Wi-fi which gives you access to a massive network of 7.5 million hotspots around the world.”

Pay as you go (PAYG) smartphone customers can make savings on their calls to mobiles, as BT’s landline rates are cheaper than standard PAYG tariffs, according to BT. They can also continue to use their smartphone to make calls when they are running out of credit.

The BT SmartTalk app is now available for free from Apple's App Store and the Google Play store, and supports up to five users on one calling plan.

The news follows the launch of an almost identical application from Virgin Media in November, called Smartcall, which allows customers to use unlimited calls from their home phone talk plan on a smartphone over Wi-Fi.

Telefonica (parent company of O2) and Orange have also launched apps that allow customers to make voice calls and send texts over data connections. Meanwhile, “over the top” services such as Skype and WhatsApp continue to grow in popularity.