Four Sutton-in-Ashfield pub licensees have been warned by Nottinghamshire Police after staff served alcohol to an under-age customer.
The young volunteer visited five pubs on Friday night and was allowed to buy alcohol in four of them.
Staff members who served the volunteer were issued with fixed penalty fines and the licensees given a warning.
Insp Andy Clarke, from Nottinghamshire Police, said: "I'm extremely disappointed with these results."
He added: "The licensees have been spoken to and warned that we will be continuing to conduct regular test purchase operations in the area.
"I expect to see a significant improvement in results, otherwise we will be forced to look at taking stronger action."