Surveillance cameras in London are not helping solve crime, according to local politicians.

The city has over 10,000 publicly funded CCTV cameras in public areas, but only one in five crimes are solved, said Dee Doocey, a spokeswoman for the Liberal Democrats political party on the London Assembly, the elected body which determines transport and policing policy for London's 32 boroughs and the City of London itself.

Using figures obtained from the London boroughs, the Metropolitan Police Service and public transport authorities through Freedom of Information Act requests, the Liberal Democrats compared the number of crimes solved in each borough with the number of CCTV cameras installed there.

"Our figures show that there is no link between a high number of CCTV cameras and a better crime clear-up rate," she said. "Boroughs with thousands of CCTV cameras are no better at doing so than those which have a few dozen."

Proponents of CCTV's usefulness usually focus on its role in preventing crime, rather than solving it. But although the cameras across London's public transport system allowed police officers to identify within a few days those responsible for the July 7, 2005, tube-train bombings in the city, the cameras did nothing to prevent the attack.

And a detailed study of 14 public CCTV installations in a 2005 report by the Home Office Research, Development and Statistics Directorate, "Assessing the impact of CCTV," concluded that "the CCTV schemes that have been assessed had little overall effect on crime levels."

Over the last decade, London's CCTV cameras have cost taxpayers there around £200 million, Doocey said, calling for a broader debate on the city's policing.