The 70cm-wide flying surveillance device, fitted with high-resolution still and colour video cameras as well as infrared night vision capability, was used to keep tabs on people thought to be acting suspiciously in car parks and to gather intelligence on individuals in the crowd.

Staffordshire police said the drone's images did not lead directly to any arrests, but one reason for using it had been to deter would-be thieves. It was not flown over the main arena because of fears that a crash might cause injuries.

The battery-operated drone's four carbon-fibre rotors are so quiet they cannot be heard from the ground once it is higher than 50 metres, and at 100 metres up it cannot be seen with the naked eye. It can fly 500 metres high, but the Civil Aviation Authority has set an operating limit of 120 metres. The vehicle, which takes off vertically, can be flown even when out of sight, because it beams images back to video goggles worn by the operator.

Since May, Merseyside police have been using two drones - originally developed by a German company for military use - to police public order situations and prevent antisocial behaviour. One tactic is to fly the drone over groups of young people causing a nuisance in parks. The force has also used it for covert surveillance.

The West Midlands fire service plans to use drones to get a bird's eye view of buildings on fire. "Being able to look down on the scene will allow us to get a full picture of the incident and the surrounding environment, which will aid incident commanders to make vital, potentially life-saving decisions," said the deputy chief fire officer, Vij Randeniya.

The Metropolitan police is interested in using drones to police the Olympics. Firearms officers also believe they could be useful in a standoff with armed criminals

MW Power, the company that distributes the technology in the UK, plans to improve the drone's capability by adding a so-called "smart water" spray - a liquid infused with unique artificial DNA sequences which can be squirted on to a suspect from above. It infuses their clothes and skin and the DNA code can be used later to identify them.

There is no legal barrier preventing a private security firm or a paparazzo photographer from using the technology, but MW Power said that it was only licensing the vehicle to customers from the military or emergency services. It costs less than £1,000 a month to lease - an amount that would buy less than an hour's use of a conventional helicopter.

Some experts fear it represents an unwarranted intrusion of privacy. "We should find out whether the public wants this," said Noel Sharkey, an expert in robotics at Sheffield University who is worried about the increasing use of robotic vehicles in military conflicts and policing. While most people would support its use to catch car thieves, the technology could be put to more draconian uses in future, he said.

"How long will it be before someone gets Tasered from the air for dropping litter, or even for relieving themselves down an alleyway under cover of night?"

· The following correction was printed in the Guardian's Corrections and clarifications column, Wednesday August 22 2007. "Smart water", the security spray mentioned above, is not infused with artificial DNA as was claimed, but with chemicals that give each batch of the liquid a unique identity.