BT Group has signalled its return to the mobile market after launching a BlackBerry-style smart-phone as part of its broadband deal for users to surf the web and make calls when not at home.

"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," said consumer managing director John Petter.

BT is among the few large telecom groups in Europe not to own a mobile network after it demerged its mobile operation in 2001.

Consumers will have a choice of two smart phones from Taiwan-based High Tech Computer Corp (HTC) which will connect to the internet at broadband speeds and provide cheaper calls when in a WiFi hotspot.

The BlackBerry email device was originally popular with business executives, but it is increasingly attracting a wider consumer market. Consumers are also moving to mobile networks and away from landlines to make their calls.

Meanwhile, employees who use mobile phones, BlackBerries or other remote technology work an extra 20 days a year, effectively giving up their holiday, according to "shocking" new research.

A survey of 1,000 staff by recruitment firm Office Angels showed that seven per cent felt under pressure and "suffocated" because they were constantly tuned in to work, while a similar number were angry that they could not switch off and escape work.

Companies are reaping huge returns by providing new technology to their staff because of the extra hours being worked, said the report.

But despite the statistics, two out of five of those questioned said they were grateful for technology, often believing it reduced stress levels by allowing flexible working and preventing email build-up.

David Clubb, managing director of Office Angels, said: "It’s important that you maintain a work-life balance and keep work in perspective. Occasionally we all need to work outside of normal hours, but this should really be the exception not the rule. Be disciplined about whether you really need to log on.