"We've had nights where we've visited 20 and had no fails, so this would be a bad night for the Wellington district.
"Licensed premises have a 'no ID, no service' policy for anyone who looks under the age of 25. As our volunteers didn't have any identification with them, the sales should not have occurred. Alcohol and young people can be a dangerous mix. We hope this operation reminds all licensed premises that controlled purchase operations can take place anytime and anywhere."
The premises could have their liquor license or manager's certificates temporarily suspended because of the sales, Mr Benge said.
Most places learned their lesson after being caught out once, he said.
"With the majority of places you find it's an oversight. They become lax or forgetful over time. It's not something they do without care and the majority that do get caught, you don't find that they fail again.
"The majority improve their processes - they certainly don't get caught a second time."
Compliant businesses would be sent a follow-up letter encouraging them to keep up the good work, Mr Benge said.