Britain is testing a CCTV system that may help identify criminals even before they offend. Critics say it's a step towards creating a society under total surveillance.

The system, already used in New York and several other American cities, automatically analyses the behaviour of people and vehicles in public places. The idea is that when the camera finds something suspicious it alerts an operator.

So, for example, people seen lurking in one area can trigger the alarm. The same happens if CCTV picks up a car moving too fast or too slow, indicating joyriding or kerb-crawling.

The human operator then checks the footage and decides whether to send a police officer to investigate, reports Britain’s Daily Mail newspaper.

“It's the 21st century equivalent of a night watchman, but unlike the human version, this one never blinks, never takes a break and never gets bored,” explained Jason Fazackarley, Councilor of Portsmouth, where the system is being tested.

There are already 4.2 million CCTV cameras in Britain, and critics say introducing this futuristic-flavoured system will infringe privacy.

A spokesman for Liberty, a human rights group, said: “Bringing expensive Hollywood sci-fi to our car parks will never be as effective as having police on the street leading the fight against crime.”

Nick Hewitson, managing director of Smart CCTV, the firm that created the technology, disagreed, saying the system is a far cry from Minority Report – the futuristic Hollywood blockbuster starring Tom Cruise featuring mutants with precognition powers that helped the police bust offenders before they committed crime.

“What it cannot do is say whether a guy is waiting for his girlfriend or about to commit a crime. That is for the operator to make a subjective human decision on,” he said.