An undercover investigation by consumer magazine Which? Computing caught branches of Woolworths, Game and Maplin in Harrow, Middlesex selling the games Grand Theft Auto – Vice City Stories, Condemned 2 and Hitman to the teenager. The Maplin store assistant asked the girl's age but did not refuse the sale when she said she was 15.
Such sales can be prosecuted under the Video Recordings Act of 1984 and punished with a fine of up to £5,000 and/or six months in prison.
Brent and Harrow Trading Standards Services, which worked with Which? Computing on the research, will not prosecute but will contact and monitor the stores, according to a statement. All three stores are investigating the findings and said that underage sales are rare.
Harrow branches of Tesco, Argos, Debenhams, HMV and Currys Digital all refused the teenager. A local shop, Entertainment Exchange, also turned her away.
In a separate investigation, Trading Standards bodies at six local authorities in Wales found nearly 90% of online traders supplying violent games to youngsters. Each authority enlisted a volunteer aged between 12 and 16 who attempted to buy 18-rated video games on the internet using postal orders.
Of the 44 test purchases attempted, 38 traders sold the games to the children assisting the authorities.
Lee Jones, acting head of Trading Standards, Bridgend County Borough Council, said the survey shows how easily children can gain access to age-restricted, violent video games.
"Traders who use auction sites and accept postal orders as payment have no method of determining whether the person they are selling to is aged 18 or over," he said.