Five knives were sold illegally to children when police carried out test purchases this week.
Officers sent police cadets aged under 18 into 16 different stores in West Yorkshire to see if staff would sell them a knife, with five shops failing the test.
Detective Chief Inspector Chris Gibson said: “It is disappointing that our underage cadets could buy knives in almost a third of shops where we carried out test purchase operations. These knives could seriously hurt someone in the wrong hands.
“We are providing knife crime awareness training to those that failed the test.”
The ongoing operation is part of a week-long #StopKnifeCrime campaign running nationally and in West Yorkshire.
It culminates today with two special events for young people in Harehills, which are being held under the banner ‘Leeds Lives Not Knives’.