It may be the best-looking piece of kit this year, but the Apple iPhone is too slow for texting, new research has revealed.

Apple iPhone users are only able to write text messages at half the speed of those using traditional numeric and Qwerty mobile phone keyboards, according to data from usability consultancy User Centric.

The Apple iPhone's touchscreen is "potentially problematic" for sending text messages, User Centric said in its ' iPhone Text Entry' report.

As part of the research, frequent texters - those who send at least 15 texts per week - tested the Apple iPhone's SMS functions to see how easy it was to adapt to the touchscreen keyboard. None of them owned an Apple iPhone. Instead, half the sample group owned a handset with a full Qwerty keyboard, while the rest used phones with numeric keyboards.

Twice as long

The testers had to type out six fixed-length text messages on their own phone, and six on an Apple iPhone. It took them almost twice as long to compose the same message on the Apple iPhone as on their own device. The time difference improved with time, but persisted even after 30 minutes' use of the Apple iPhone.

"For Qwerty users, texting was fast and accurate. But when they switched to the Apple iPhone, they were frustrated with the touch sensitive keyboard," said Jen Allen, a usability specialist at User Centric.

When using the Apple iPhone's touch keyboard, all participants frequently selected keys that they had not intended to select.