Last week the Guardian revealed that the number of police ANPR (automated number-plate recognition) cameras in this country has almost doubled over the last three years; as a result, there are now more than 8,000 of these cameras monitoring the UK’s roads.

This is just the latest example of the way in which CCTV has become increasingly ubiquitous, leading to estimates that there may now be as many as 5.9 million cameras in the UK. While the vast majority of these are operated by the private sector, significant public resources have also been invested into building a network of CCTV camera across the UK. But is this money well spent?

Our recently-updated briefing on CCTV examines the evidence supporting its efficacy, and the picture is far from clear. Certainly the police believe that CCTV helps prevent crime and catch criminals. The public is also supportive. 93 per cent of the public support the use of CCTV in banks, 86 per cent outside pubs and 84 per cent on high streets. 81 per cent believe it helps the police to fight crime.

However, while a thorough review of the evidence found that CCTV has a modest but significant desirable effect on crime’, it also noted that this was primarily based on evidence that CCTV cameras in car parks reduce vehicle crime specifically. Schemes in city and town centres, as well as those on public transport, did not have a significant effect on crime. The review concluded that CCTV should be more narrowly targeted than it currently is.

In addition there is little research evidence to support the widespread assumption that CCTV helps the police to detect crime. Similarly, while the police believe that ANPR cameras are an important crime-fighting tool, there is no research that has rigorously explored the link between ANPR and the disruption of serious criminal activity. Nonetheless the use of CCTV is clearly central to some cases and it can play a key role in securing a conviction or an early guilty plea. Technological advances are also likely to make it increasingly effective in this area.

There are also issues to consider that go beyond CCTV’s efficacy in reducing crime and helping the police to identify offenders. Civil liberties groups argue that the current use of CCTV is excessive, generating a huge quantity of data on ordinary citizens, while in 2006 the then Information Commissioner stated that uncontrolled or excessive surveillance can foster a climate of suspicion and undermine trust’. There is also little evidence that CCTV reduces the fear of crime, with some researchers even suggesting that it could increase it.

None of this is to suggest that there is not an important role for CCTV in local crime prevention. Nor should the rapid expansion of ANPR cameras necessarily be seen as a bad thing. But when considering whether and where to use CCTV, the police and local authorities should be aware of its limitations and ensure that cameras are deployed proportionally, are effectively targeted, and are used alongside a range of other crime reduction measures.