Councils have spent more than £500m installing and operating CCTV cameras over the last four years.

Local authorities have installed cameras at such a rate there are now at least 51,600 in operation - 50 per cent more than previously thought.

The figures have been released by campaign group Big Brother Watch, who say there is no evidence to suggest that more cameras are cutting crime.

The group's director Nick Pickles said the data, obtained under the Freedom of Information Act, shows the UK has a "surveillance culture" which is out of control.

"It comes at a cost to our privacy," he told Sky News.

"We think we need a national review now to establish if councils are using their cameras properly."

The figures from the 428 local authorities that provided data show five councils now have more than 1,000 cameras each.

Since 2007 Birmingham and Westminster councils have each spent more than £10m on CCTV, while another 16 authorities have each spent more than £1m per year.

Mr Pickles says the total cost to UK local authorities would put an extra 4,121 police constables on the streets - the equivalent of the entire Northumbria Police force.

"We found there's a widespread belief that cameras deter crime but if you look at the academic research, that's simply not the case," he said.

"If you look at research into car parking, cameras proved useful. But if you look at street crime, street lighting proved more effective.

"We think it's important to consider cameras as part of response to crime, not as in some cities, a substitute for police."

Figures compiled last year for the Association of Chief Police Officers (ACPO) by Cheshire Police Deputy Chief Constable Graeme Gerrard estimated there were 31,000 council-controlled cameras.

In a statement released by ACPO, DCC Gerrard said cameras help solve crimes and are of "critical importance".

"Overall, ACPO believes the contribution of CCTV to the detection of crime is comparable to that of DNA and fingerprints," he said.

Coun Peter Gruen from Leeds City Council, which has spent £8.7m on CCTV - the third highest figure in the country - said the cameras improve public confidence and safety.

"[CCTV] is one of the most helpful tools we have for deterring crime and bringing offenders to justice," he said.

"We believe that it is money well spent and that many members of the public feel it offers a tangible way of feeling safer."