A team at the University of Michigan claims to have found evidence that violent computer games can harm children.

The news comes just 24 hours after the British Board of Film Censors admitted that there is no evidence to suggest that violent computer games promote actual violence in those who play them.

University of Michigan researchers L. Rowell Huesmann and Brad Bushman analysed 50 years of studies, and concluded that violent computer games are a major public health threat as they raise the aggression levels of those who play them.

The analysis, published in the Journal of Adolescent Health, claims that the problem is second only to lung cancer caused by smoking.

"Exposure to violent electronic media has a larger effect than all but one other well known threat to public health," Huesmann told Reuters.

"The only effect slightly larger than the effect of media violence on aggression is that of cigarette smoking on lung cancer.

"The research clearly shows that exposure to virtual violence increases the risk that children and adults will behave aggressively."

The research suggests that children who play violent video games and identify with the characters are much more likely to be more aggressive in social situations when older. The effect is the same for men and women.

Huesmann admitted that not all children are affected, but that controls are needed anyway.

The study was co-funded by the US Centre for Disease Control.