The Bay of Islands has come up trumps again in the latest controlled purchase operation, where 16-year-old volunteers attempted to buy alcohol at 16 licensed outlets.
No sales took place.
It was a different story in the Kaipara though, with four of 18 outlets selling alcohol to the teenagers.
Alcohol harm reduction officer Sergeant Howard Clement said the Kaipara result was disappointing.
"The premises involved should have better systems in place regarding not selling alcohol to minors. These sales of alcohol should not be occurring," he said.
"All applicants, when they make application for a licence to sell alcohol, state that appropriate systems and procedures are in place to prevent sales of alcohol to underage people.
"As a community we need to have confidence that licence holders will not sell alcohol to our youth and allow them [to drink] unsupervised and potentially harmfully."
Breaking the law could result in licence suspension for several days.
Sergeant Clement's counterpart in Kerikeri, Senior Constable Graeme Wright, described the outcome there as another excellent result.
It is the sixth CPO carried out in the Mid and Far North this year without a single sale.
He emphasised that alcohol should not be sold to anyone who appeared to be younger than 25 who could not produce identification.
It was important that a full and proper identification check be carried out, including calculating the customer's age.
"This is best practice, and the only sure way to prevent (illegal) sales, but overall I am encouraged by this result.
"It demonstrates that our off-licence premises are responsible holders of liquor licences and are protecting the young people in their communities."