Nearly 700 people have been caught driving under the influence of drugs since anti-drug-driving laws were introduced in November 2009.
The figures have led the Automobile Association to declare an epidemic.
Topping the country's drug-driving statistics is the Bay of Plenty, where 139 drivers have been charged for driving under the influence of drugs since the law came into force.
But AA spokesman Dylan Thomsen said if police in other districts carried out the same number of tests, the results would likely be similar.
"The police in the Bay of Plenty have actually made this a focus and have been doing more tests. I would say it's a credit to the Bay of Plenty police that they are targeting the issue, but it's just the tip of the iceberg," Mr Thomsen said.