First there was closed-circuit TV. Then speed cameras. Then DNA profiling, plans for ID cards, and cellphone data storage.

In March, Britain will enhance its reputation as the surveillance capital of the West with a global first: recording the movements of all cars on the road and storing the data for at least two years.

It's a network of thousands of cameras harnessed to software that can read car license plates, check them against a central database, and alert police to suspected criminals or terrorists.Police chiefs are thrilled at the technology, arguing it will provide an unrivaled crime-fighting tool that will also aid antiterror efforts.

In regional trial runs, the number of arrests per officer shot up from around 10 per year to 100 per year. Convictions also increased.

But civil liberty activists are aghast at yet another move by the authorities to spy on citizens in the name of security and law and order, warning of a growing bank of Orwellian technology.

"The freedom and anonymity of the open road is something that is culturally important here," says Simon Davies, director of Privacy International. "Now like some scene in '1984,' the fact that we will travel and be detected and analyzed changes the whole psyche of the nation."

In their defense, police say they need the best technology available to reduce perennially rising crime rates and face an acute terror threat.

"Criminals use cars, it's as simple as that," says John Dean, a retired officer who is coordinating the rollout of the automatic number plate recognition (ANPR) program.

"It's taken a while to get the police service to realize that this can make a significant difference to crime detection and terrorism."

Same cameras, new cross-checking

Britain's 30 million motorists have long been used to assiduous roadside camera surveillance, be it to deter speeding or monitor London's congestion charge - an £8 ($14) fee charged for driving into central London during business hours.

But the ANPR nationwide system will use the extensive camera network already in place as well as new cameras to capturelicenseplates from as many as 50 million cars a day and store them in a vast databank with date, time, and location stamps.

Within a matter of seconds, the database will signal whether the car may be of interest to police, cross-checking the plate against a list of stolen and suspect vehicles and also verifying for proper insurance, taxation, and roadworthiness. Dedicated ANPR operators will then alert roadside units to the rogue vehicle.

"People who drive stolen cars often steal them as a result of burglary," says Mr. Dean, so you might find property in the back or other material. It's very efficient."

Police say life is about to get tougher for criminals, whether they are involved with drugs, firearms, identity fraud, or property theft.

Or terrorism. At least one vehicle was used to convey the July 7 bombers and their materials part of the way to London last year. Police are not saying that ANPR would automatically have foiled the plot. But Dean says the technology, already in use at a local level in some parts of the country, had brought "benefits to the investigation."

Tracking movements over a long period

Even if an immediate arrest is not possible, the data will help the authorities build up an intelligence picture of the movements of suspicious vehicles and analyze journeys that drivers have made over several years. The intelligence service MI5 will also use the database, according to Frank Whiteley, a senior police officer.

But not everyone thinks that trusting cameras and cops is a good idea.Already in Britain there is a fierce lobby opposed to the proliferation of speed cameras, which many see as a tool of the tax man rather than a road safety enforcer.

Some wonder whether ANPR, which will cost tens of millions of pounds to set up, will be used primarily to drum up fines and revenues from road-tax delinquents.

Nigel Humphries of the Association of British Drivers lobby group worries that "real criminals have cars that can't be traced anyway." He says the system may offer benefits, but "there need to be safeguards."

Parliament should have oversight

Edward Garnier, a Conservative MP and spokesman on home affairs, says that Parliament, not the police, should act as arbiters over the system because of its implications for the criminal justice system and for civil liberties.

"I can understand why the police want to use this technology but they should not be the arbiters," he says.

Privacy and civil liberty champions take a more fundamental opposition to the scheme. Mr. Davies of Privacy International, likens it to "weeding with a bulldozer."

"So long as you believe that every person in government and authority is just and fair and that the machinery of the state never screws up, then it's fine," he says. In fact, the ANPR technology has fallen well short of a 100 percent score in policing London's congestion fee. Other police databases have similarly proven fallible.

Opponents of surveillance say Britain is rapidly emerging as the biggest of Big Brother societies, a "database state" with an increasing tendency for automated answers to social questions.

The government still plans to use biometric identity cards beginning in 2008, together with a national database. A national DNA database already has samples from 1 in 10 British adults, more than 100,000 of whom have never been charged or even cautioned. And last month, Britain persuaded its European partners to join it in storing data from cellphone records for up to two years as a counter-terrorism tool.

And it may not stop there.

Experts are already working on systems that can automatically recognize human faces and it may not be long before machines can pick out a "suspicious" face in a crowd. Many on both left and right of the political spectrum find the growing use of surveillance disturbing.

"Frankly I don't want to see a society in which the Big Brother element comes to the fore," says MP Garnier