There is "scant scientific evidence" that video games encourage violent behaviour, new research reports.

Patrick Kierkegaard, of the University of Essex, argues in the International Journal of Liability and Scientific Enquiry that video games are "harmless" and do not lead to real-world aggression.

Moreover, he claims that previous research work has been unfairly biased against video games.

The publication of the research coincides with the launch of the controversial Grand Theft Auto IV which features scenes of murder, theft and destruction.

Kierkegaard points out that these violent games are growing more realistic with each passing year, and that most relish their plots of violence, aggression and gender bias.

But the academic questions whether there is any scientific evidence to support claims that violent games contribute to aggressive and violent behaviour.

Kierkegaard studied a range of research papers published since the 1980s, several of which concluded that video games can lead to juvenile delinquency and violent criminal behaviour.

Evidence from brain scans carried out while gamers play also seems to support a connection between playing video games and activation of regions of the brain associated with aggression.

However, Kierkegaard maintains that there is no obvious link between real-world violence statistics and the advent of video games.

In fact he argues that the effect seems to be the "exact opposite" and that it could be argued that video game usage has reduced real violence.

"Violent crime, particularly among the young, has decreased dramatically since the early 1990s, while video games have steadily increased in popularity and use," said Kierkegaard.

"For example, in 2005 there were 1,360,088 violent crimes reported in the US compared with 1,423,677 the year before.

"With millions of sales of violent games, the world should be seeing an epidemic of violence. Instead, violence has declined."

However, Kierkegaard emphasised that the research is inconclusive. It is possible that certain types of video game could affect emotions, views, behaviour and attitudes, but books can also lead to violent behaviour in those already predisposed to violence.

The inherent biases in many of the research studies examined by Kierkegaard point to a need for a more detailed study of video games and their psychological effects.