Unmanned police spy drones could soon be flying over Kent - if investigations prove their worth.

Police have confirmed they are investigating the use of the drones to carry out routine surveillance and monitoring.

The force said it had no immediate plans for their use but was examining if the technology, adapted from military planes, had potential.

The prospect of police forces using spy robots, manned from the ground, has already triggered concern about civil liberties and as further evidence of the growth of a "Big Brother" state.

According to a report in The Guardian, Kent Police’s assistant chief constable Allyn Thomas wrote to the CAA (Civil Aviation Authority) in March last year arguing that drones would be useful "in the policing of major events, whether they be protests or the Olympics".

Mark Reckless, a member of the Kent Police Authority and a Conservative prospective parliamentary candidate in Kent, said he would need to be convinced it was cost effective and proportionate.

"In principle, I do not have objection to the force looking at it and keeping it under review. But I am far from convinced that it would be cost-effective. There are issues around privacy and that would have to be a consideration. The question is whether using a drone would be proportionate to any of the benefits that might come from it?"

Kent Police is heading a consortium of government agencies, known as the South Coast Partnership, to consider the possible use of spy drones.

Initially, one of the aims was to examine how they might be used by the police and border agencies to carry out surveillance and monitoring across the channel.

However, that has now developed and they could now be used to police major events, such as large public protests and the forthcoming Olympics in London.

In a statement, Kent Police said: "We have been looking at new police aviation technology and the possibilities it can offer us in terms of border and maritime security. Kent Police does not currently use unmanned aircraft systems and we have no plans to start using them in any aspect of the policing service we provide."

The technology is being developed by BAE Systems, the multinational arms company which says it could be available by 2012.

One obstacle is that the Civil Aviation Authority has yet to licence drones in airspace because of the risk of collisions with aircraft.