The £2.9bn Airwave radio system, designed to improve communications across the emergency services, will require significant extra investment to meet its original objectives, according to experts involved with the project.

Airwave has been struggling for months to deliver more than limited access to police computer systems, and concerns remain over its reliability.

Data transmission speeds currently vary between 3.2Kbps and 7.2Kbps, still far short of the 28.8Kbps promised, restricting the use of planned functions such as accessing pictures and fingerprints.

"The whole thing about Airwave was data; that was how they sold it to us," one former chief constable, who sat on the technology and research committee for the Association of Chief Police Officers, told vnunet.com's sister title Computing.

Airwave promised to eradicate blackspots in the radio network, and release officers from having to return to police stations to perform data input tasks.

Insiders claim that the number of radio masts needs to double from 3,000 to 6,000, and that police will have to replace many existing handsets because changes in technology have rendered them obsolete.

"Some of the older model terminals would need to be upgraded in order to display a picture on the handset," said a spokesman for the Police Information Technology Organisation.

But the problem may be more widespread, and technicians have indicated that they are struggling to provide pictures.

"We have it working so that we send a roughly recognisable passport-sized picture, but it is very slow," said one technician.

But an expert on police radio systems added: "The current technology cannot handle pictures or video. In fact, I do not think it ever will."

Jeff Parris, vice president of the network's operator, Airwave mmO2, acknowledged that data capabilities are key to the system.

"It is up to each police force, fire brigade and ambulance trust to decide how to implement [Airwave]," he stated.

Some forces are voting with their feet and turning to GPRS-based systems. Staffordshire, Durham, West Yorkshire and North Wales police have all conducted trials.

Liberal Democrat Home Affairs Spokesman Mark Oaten is to table a series of written questions in parliament over the effectiveness of Airwave.

"We want our police to have the very best equipment to help them in their fight against crime," he said.