Police have admitted patrolling at night without car lights on, a breach their police chief earlier denied.

Nelson Bays area commander Inspector Steve Greally has admitted that some of his officers may have violated traffic laws and operating procedures while on patrol in Takaka at the end of last month.

His change of position follows his earlier denial of any wrongdoing, but subsequent conversations with officers has led him to open an investigation into charges that police were entrapping motorists by driving without headlights.

In a response to a letter to the editor published in the Nelson Mail on February 28, from Takaka resident Steven Wilkinson exposing the practice, Greally wrote then: "Having spoken to all staff involved I have complete confidence that no police vehicles were driving with lights off during darkness.

"This is not a procedure police would condone."

Now Greally said: "I felt really bad when I said what I said and now that I have spoken with the right people, some of my officers said `Hey, this happened'.

"Driving round purposely without lights on is a no-go. It does not align with our high visibility strategy."

Greally speculated officers may have made the mistake of leaving lights off in a well-lit area.

Ngawai Campbell-Joyce, 19, was pulled over in central Takaka, far from the streets lights of town, on February 18 by a police car without headlights on.

"They just came out of nowhere," said Campbell-Joyce. "When I got to the hospital corner, all of the sudden there were coloured lights flashing behind me. He was trying to trap me."

Campbell-Joyce said the incident happened at 11.30pm and the night was dark without any moonlight. He was breathalysed, questioned, and then allowed to drive his friends home. It was his first experience with police and he did not think to question the officer as to why he did not have headlights on.

In Takaka, Craig Haisty, owner of the Roots Bar in Commercial St, saw the police use a similar tactic as they searched some of his clients on the street.

"I was standing at the door and I saw a car coming towards us and I said to my friend, `Look at this, there's someone driving down the road with no headlights on' and then the next thing I know they pulled in at a big angle in front of the bar."

Haisty said the officers forced a group of tourists to empty their bags and their pockets. No charges were filed against the tourists.

"They were fairly rough," he said. "It was pretty heavy the way they skidded and jumped out. Obviously they were sitting out there watching what was going on."

The officers now under investigation were over from Nelson as part of the Traffic and Alcohol Group to combat drink-driving and disorderly conduct. Haisty emphasised that these were not local policemen.

"The local guys don't act like that, that's for sure," he said. "The local guys are really good policemen."

Wilkinson, who drew police attention to the reports of misconduct in his letter to the Nelson Mail, maintains the events on February 18 were not a one-off.

"It seems to be a common occurrence here where the police have been driving around without headlights on," Wilkinson said. "Residents have seen the local pursuit car travelling at night-time down Commercial Street travelling like a shark, no headlights on."

While he is pleased to see an investigation taking place into the reports of misconduct by police, Wilkinson says the public has an obligation to be vigilant and vocal. "I strongly believe that the community should be policing the police because if we don't, then nobody else is going to."

For Greally, this is a serious matter and he agrees that no officer is above the law. "If we're trying to uphold the law we cannot be seen to be breaking it ourselves," he said.

"I'm taking it seriously and if this has occurred we will rectify it. People need to have confidence in the police that this is above board and transparent."

Greally said the outcome of the inquiry would be clear in a week.