Five shops are under investigation after knives were sold to 13-year-old girls.
Two children went undercover for Bury council and visited 50 shops, pubs and gambling premises over the Easter school holiday.
They attempted to buy a variety of age-restricted products such as knives, alcohol, cigarettes, e-cigarette liquids and DVDs as part of the trading standards operation.
They also tried to play fruit machines.
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The girls were turned away at 30 of the businesses, but they bought seven knives from five retailers without being asked for ID.
Bury council said the five shops are being notified and investigations are under way.
Angela Lomax, head of trading standards and licensing at Bury council, said: “The results of the test purchase operation are disappointing.
"It’s absolutely vital that retailers and licensed premises in the borough have measures in place to prevent under-age sales of all age-restricted products, but in particular knives, given the current problems relating to knife crime nationally.
"Staff should be properly trained to prevent knives getting into the hands of children.
“We are committed to working with our partners including Greater Manchester Police to combat the problem of knife crime, and will be taking relevant action against the retailers who failed the operation.”
