The survey findings challenge government anti-crime policy that involves spending pounds 170m on fitting thousands of surveillance cameras in urban areas throughout Britain.
Results from three accident and emergency departments in Wales showed varying success rates for CCTV systems in preventing violent crime.
Surveillance cameras are now considered a crucial deterrent in the battle against crime, although some critics argue the system is still unproved and that there are more cost effective ways of tackling lawlessness.
The study found that in the North Wales seaside resort of Rhyl, and in Swansea, the number of people needing medical attention for violent assaults rose by 45 per cent and 3 per cent two years after CCTV was fitted. In Cardiff, the level of injuries from violent incidents dropped 12 per cent.
The number of assaults recorded in the two years before cameras were fitted in Swansea was 3,967, rising to 4,086, in the two years following their installation between December 1994 and January 1996. In Rhyl assaults rose from 1,249 to 1,823. Cardiff, however, saw offences drop from 7,066 to 6,251. Overall CCTV installation was associated with a 1 per cent reduction in assaults recorded by A&E departments.
The study, published yesterday in the Journal of Accident and Emergency Medicine, suggests the rise in injuries is partly due to cameras deterring many outdoor assaults. Many now take place behind closed doors, particularly in pubs and clubs.
There were discrepancies between the police-recorded figures for crime and the attacks dealt with by hospitals, suggesting that many assaults are not reported to police. In Swansea only one in nine offences leading to accident and emergency department treatment was recorded by police.
The report, Effect of closed circuit television on urban violence, carried out by the Violence Research Group at the University of Wales College of Medicine in Cardiff, concludes: "City centre CCTV installation had no obvious influence on levels of assaults in A&E departments. [The results suggest] that CCTV is not effective on its own but must be combined with strenuous police efforts to record the offences and prosecute the violent offenders which CCTV brings to light."
Under the last government, pounds 39m was spent on CCTV. Labour announced in March that pounds 170m - enough for 40,000 cameras - has been allocated for CCTV during the next three years. The cameras will focus on crime reduction, particularly on problem housing estates, car parks, and town and city centres.
A Home Office spokeswoman said: "We do not pretend it [CCTV] is a panacea to crime, but used in the right conditions along with a package of other measures, such as targeted policing, it is proven to work."
She gave as an example the town of Crook, Co Durham, where recorded crime in the town centre fell by 68 per cent in the 16 months after the arrival of CCTV in August 1997.Reuse content