The Police Conduct Association says the Michael Blowers case raises questions about how common drug offending is in the police.

The Former Whangarei detective has now pleaded guilty to the theft of methamphetamine from a police store...and then supplying the drug to a dealer.

Police Conduct Association President Shannon Parker says with another case of a similar nature in Huntly, there's concern at how much of offending might be going undetected.

She says there have also been cases where drugs haven't even made it as far as the lock-up room.