Manhunt should only be sold to people aged 18 and over

County council trading standards officers are mounting a campaign against traders who flout age certificates.

Teenagers posing as customers will visit shops with a view to issuing warnings or bringing prosecutions.

The action comes after the murder of a teenager which the victim's parents claim was inspired by the game Manhunt.

However, the police have denied any link.

Some of the more violent games on the market involve multiple killing sprees, put players into the role of contract killers and encourage them to run over pedestrians Mick King, trading standards officer

Trading standards bosses in Northumberland have urged parents to back their campaign.

Mick King, trading standards officer, said: "Like films, video games have age ratings, but we find that there is less awareness of this among retailers because violent video games are still quite new.

"It's not all Mario these days - some of these games have adult content and violence which most parents would not want their children to see.

"We are reminding traders that they have a duty to uphold the certificates and risk a court case if they sell over 18 games to children - they are clearly marked and there is no excuse.

Issuing warnings

"Some of the more violent games on the market involve multiple killing sprees, put players into the role of contract killers and encourage them to run over pedestrians.

"We would hope that parents would back us on this.''

Under-age investigators have previously helped uncover sellers of over 18s videos and shops selling aerosol paint to children.

The squad pose as customers wanting to buy products only available to over 16s or 18s and play a vital role in issuing warnings or bringing prosecutions.

A number of major high street stores have withdrawn the Manhunt game from sale.

Academic opinion over whether such games can affect adolescents is mixed, but many researchers say watching violent cartoons or games does alter younger children's behaviour in the short term.