There was no history of southern district officers hiding in rental vehicles and spying on country hotel patrons, and no plans to implement such such activity, southern district communications manager Vivien Pullar said.
Hurunui police supervisor Sergeant Graeme Crosson confirmed the measure was used in North Canterbury for the first time last month in a major campaign against drink-driving.
Money provided by the Accident Compensation Corporation partly funded the rental vehicles.
Sgt Crosson said two intoxicated drivers were detected directly as a result of covert surveillance at licensed premises.
Police targeted drivers in Hanmer, Culverden, Waiau and Leithfield.