BT Group has dived back into the mobile market with an offering squarely aimed at the BlackBerry and the iPhone.

Like the popular smartphones from RIM and Apple, the so-called BT ToGo allows customers to browse the internet and make calls. But BT’s device automatically switches between the internet and its mobile network depending on where the user is.

The ToGo, which is part of the group's new broadband package, BT Total Broadband Anywhere, runs off BT's home hub broadband inside the home, while using the group’s WiFi zones and its mobile network - which it hires from Vodafone - when out and about. Customers get unlimited internet access at home or within one of BT’s 2,500 WiFi zones and 82,000 BT FON WiFi hotspots, plus a limited number of free mobile minutes and texts and a 10 megabyte monthly limit on downloads when using BT's mobile network.

Made by Taiwanese manufacturer HTC, the ToGo also allows users to make cheap VoIP (voice over internet protocol) calls and connects to the internet at broadband speeds.

Customers will be given their own mobile number or can opt to have their number ported over from their current mobile provider to BT.

John Petter, managing director of BT's consumer division, said: "Communications services are converging, and it is clear that customers want consistent access to the things that matter not only at home, but in the palm of their hands wherever they are."

With 4.25 million customers and a 25 per cent market share, BT is the leader in the UK’s fiercely competitive broadband market, followed by Virgin Media and Carphone Warehouse’s TalkTalk.

Yet it is one of the few large telecoms groups in Europe that does not have its own mobile network, after spinning off Cellnet, its mobile division, which later became O2, in 2001.

With mobile operators launching 3G dongles, which provide mobile broadband for laptops, and predicting the end of the fixed line, BT is now fighting back.

The Broadband Anywhere strategy was developed under the watch of Ian Livingston, head of BT Retail who will take over as chief executive from Ben Verwaayen at the end of this month.

It is not the first time the telecom giant has attempted to re-enter the mobile market.

In 2005 it launched BT Fusion, its first attempt to straddle the gap between mobile and home telephony, but it attracted less than 50,000 customers.

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