An undercover Trading Standards operation in Dundee found that three-quarters of stores were willing to sell 18-rated games to an underage shopper.
A 14-year-old volunteer managed to purchase an 18-rated game at 12 out of 16 stores targeted, even though some tills gave staff pre-programmed warning prompts.
Gamestation, Game, PC World and WH Smith were the only stores to pass the test.
"It is very disappointing that so many large retailers have ignored their own systems in regard to restricted video game sales,” a Trading Standards spokesman told the BBC.
Councillor Jimmy Black added: "They place themselves at serious risk of further investigations by our officers."
The maximum punishment for the offence is six months in jail and a fine of £5,000.