Senior officers are about to launch a Christmas crackdown on anti-social behaviour, but say the actions of a minority could frustrate their efforts to maintain law and order.
It follows the arrest and fining of a 41-year-old woman from the Alnwick area, who admitted supplying booze to juveniles.
Inspector Sue Peart said: "Groups of youngsters who have been drinking cause problems, make life unpleasant for others, but also become vulnerable themselves.
"We are trying our best to prevent this from happening, but there are a few extremely irresponsible adults out there who are providing these kids with alcohol.
"What kind of person would do this beggars belief, but it is happening, as this latest arrest shows."
She added: "Make no mistake, we will come down very hard on anyone who is found to be supplying alcohol to anyone under the age of 18.
"I hope that this demonstrates we are absolutely committed to doing everything we can to stop the scourge of alcohol-fuelled anti-social behavior by children."
As well as prosecution, offenders can expect fixed penalties, while shop staff who sell to juveniles are liable to lose their personal licences.