The skies could soon be filled with the buzzing of thousands of tiny spy drones trained to snoop on British streets, the Home Office has warned. They are one of a number of futuristic snooping techniques that could become reality including CCTV that recognises faces and cameras in the back of taxis.

The warning comes as the Pentagon revealed it is pumping hundreds of millions of dollars into new drone technology such as the 'nano-hummingbird' - a tiny remote helicopter equipped with video and audio equipment that can record sights and sounds.

Ministers said that advances in technology have meant such hi-tech measures are now possible and could soon be ubiquitous across the country.

It said: 'Modern digital technology is on the cusp of revolutionising the use of CCTV. The consultation said powerful zoom features, 360-degree vision and facial recognition 'are coming closer to being an established part of the CCTV landscape'. It continued: 'New uses for systems, for example in taxis, are a natural part of industry growth.'

Britain is one of the most watched countries in the world with one CCTV camera for every 14 people.

The U.S. government has announced plans to develop tiny drones and large unmanned aerial systems for its armed forces.  Many are inspired by nature and are designed to look like birds, so they blend seamlessly into the sky, such as the nano-hummingbird by California-based technology firm AeroVironment.