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 MoD is carrying out research and development to enable the spy planes, which are equipped with highly sophisticated monitoring equipment that allows them to secretly track and photograph suspects without their knowledge, to be deployed within three years.
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.
The unmanned aerial vehicle (UAV) can obtain clear images while flying at up to 50,000ft. If ministers give the scheme the go-ahead the UK will be among the first countries to use UAVs to monitor its own citizens.
The Israeli military operates them over Palestinian cities such as Gaza and Ramallah, while the US Customs and Border Protection agency flies them over the Mexican border to detect illegal migrants along specified routes.
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."
UAVs are currently restricted to military installations in Salisbury Plain because of regulations banning them from using the same airspace as civil aircraft. However, a commercial consortium led by BAE Systems will provide the safety measures necessary for the planes to fly over the UK within three years.
The MPs' report says the MoD is "closely involved with the development of procedures and regulations which allow UAVs to operate in national and Nato airspace. But the committee indicates that the ministry should do more."
The BAE Systems consortium is partly funded by a number of government agencies, but not the MoD, which has an observer status on the project, called the Astraea programme. The next stage of the project is due to cost £44m, with private companies providing half of that.
The committee says: "In the response to our report we expect the MoD to set out why it supports the Astraea programme only in an 'observer role' and its future plans with regard to this programme."
The MPs say full consideration should be given to evidence given to the committee by a weapons company that meeting the air safety requirements would open the way for UAVs to be used in disaster relief, crowd control, anti-terror surveillance, maritime searches and support for the Coastguard, police, fire and intelligence services.
The UAVs will give law enforcement agencies huge scope for surveillance. Robert Emerson, a security analyst who specialises in deciphering aerial images, said: "Satellite images can be affected by clouds and lack of light, with UAVs you can avoid that by choosing the height at which you fly. There is now also Google Earth, but these are often old images out of date. There is tremendous potential in material gathered by UAVs."
He added: "There will obviously be implications for privacy, human rights, etc. That is something the Government will have to address and I imagine that there will be protests from some quarters. But you certainly cannot blame police and intelligence services for wanting to use them."
There are also concerns over safety, however. In April 2006 a UAV used by US Customs and Border Protection crashed in Arizona when its engine was accidentally turned off by the team piloting it. At the end of the first investigation into an un-manned aircraft accident, America's National Transportation Safety Board issued 22 recommendations and its chairman talked of a "wide range of safety issues involving the civilian use of unmanned aircraft".
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