BlackBerry maker Research In Motion (RIM) has officially unveiled its first touch-screen smartphone, designed to compete in the consumer space with rivals such as Apple's iPhone as well as appeal to RIM's corporate user base.

The BlackBerry Storm, set to be available in the UK before Christmas, does away with the physical keyboard of other BlackBerry models and instead uses a larger touch-sensitive screen.

The handset will be available through Verizon Wireless in the US and Vodafone in the UK, the latter offering it for free on a £35 tariff.

RIM said that the new device has been designed around ease of use, and offers a more compelling multimedia experience for users.

"It is a credible consumer device with a music player, it lets you download music over-the-air, and it has GPS that supports turn-by-turn navigation," said Rob Orr, RIM's director of carrier product management.

Particular attention has been paid to the touch screen, which gives the user positive feedback when they select an item or hit an on-screen button.

"We took the technology of the capacitive screen and added a switch so you can press the screen and it 'clicks'," said RIM president and chief executive Mike Lazaridis.

"You get mechanical feedback, so you don't have to worry about accidentally triggering something just by touching the screen."

Although the BlackBerry Storm has no physical keyboard, users can key in text using one of two on-screen 'soft' keyboards: a full Qwerty or RIM's more compact SureType style.

The device has the new-look user interface introduced on the BlackBerry Bold and, like other RIM models, has support for the BlackBerry Enterprise Server and BlackBerry Internet Service for email access.

In specification, the BlackBerry Storm is a quad-band GSM handset supporting HSPA up to 7.2Mbit/s on 3G networks in the UK. The US model additionally supports CDMA and EVDO, according to RIM.

However, there is no Wi-Fi support. "We just couldn't fit Wi-Fi in along with everything else," said Lazaridis.

The phone has a 480 x 360 pixel display and 128MB memory, with storage expansion via a MicroSD card slot located under the rear cover. The battery is a 1400mAh lithium cell rated at 15 days on standby and six hours of talk time.