The Government is drawing up plans to use unmanned "drone" aircraft currently deployed in Iraq and Afghanistan to counter terrorism and aid police operations in Britain.
The plans have been backed by the House of Commons Defence Committee but have attracted criticism from civil liberties campaigners concerned about the implications of covert surveillance of civilians.
Gareth Crossman, director of policy at the civil rights watchdog Liberty, said: "The question is not so much about the technology but what one does with it. We have quite definite laws about where CCTV can be used but of course with UAVs you have much greater ability to gather material in private spaces and this would lead to concern."
He added: "If they are used to simply hover to gain random information then that would obviously be a matter of worry and a civil liberty issue."