Children were able to buy age-restricted computer games with "alarming" ease, trading standards officers in County Durham discovered.
Undercover 13-year-old volunteers visited 10 retailers and attempted to buy both 15 and 18 classified games.
They were able to make successful test purchases in half the outlets, which ranged from supermarkets to video and electronic goods shops.
These are now being investigated under the Video Recordings Act.
'Sex and violence'
Phillip Holman, Durham County Council's head of trading standards, said: "Increased use of video clips in video games means that many more computer games are now covered by age restrictions.
"Many clips contain scenes of sex and violence and are therefore given an age rating in the same way that films are classified. These games are deemed not suitable for young children.
"It is essential that sellers of all age-restricted products ask for proof whenever they are in any doubt about a person's age. This is the only sure way of preventing these goods falling into young hands."
The move follows previous operations centred on underage sales of tobacco and alcohol.