Police from 39 forces in England and Wales took to the streets from Feb 8-24 as part of a £760,000 campaign to cut levels of under-age drinking.
Children found with alcohol were asked to hand it over to officers who also asked for their age and where they had got it from.
Of those who were found with alcohol, 15% said they had bought it from a shop themselves, 5% said they had asked a friend to buy it and 4% persuaded a stranger to buy it. Another 5% took alcohol from home, with 1% admitting they were given it by their parents.
Police could not get 30% of offenders to divulge where their alcohol had come from and 40% of results were unknown.
Home Office minister Vernon Coaker said he wanted to send a "strong signal once again to those persistent few irresponsible retailers that deliberately sell to under-18s.
"They will be caught and they will be punished," he said.
However, he also said parents needed to be more responsible for their children.
He said: "Where poor parenting is identified as an issue I want to see greater use of parenting contracts to tackle persistent under-age drinking. I also want to see greater sharing of information between police and local agencies about repeat offenders to address problems as early as possible."
The Association of Convenience Stores praised the police for targeting the children who were drinking.
Chief executive James Lowman said: "At last police time has been dedicated to tackling under-age drinkers themselves. We believe that measures such as these show to under-age drinkers that there are consequences to their actions. But we need more enforcement against those buying alcohol when under-age or proxy purchasing on their behalf.”
The Wine & Spirit Trade Association announced earlier today that Children's minister Kevin Brennan would be talking about ways to cut under-age drinking at its spring conference.
“Our experience of working in partnership with police, trading standards and retailers suggests that increased co-operation can produce results,” said WSTA chief executive Jeremy Beadles.