A police officer will appear in court on a disorder charge after allegedly verbally abusing a woman and her young son while on a night out drinking with a colleague.

The Herald understands the two officers were detained in the early hours of Saturday in Papakura.

One of the men is alleged to have approached a woman in a parked car and demanded her name and address.

When she refused, he allegedly told her he was a police officer and pressed his badge against the windscreen.

The woman - whose 11-year-son was in the back of the car - again refused to give the pair her details and told one of the officers that his fly was down.

The Herald understands one of the officers is alleged to have then exposed himself to the woman and her son.

The woman crossed the road to a petrol station and asked for help from one of the staff, who called the police.

The two off-duty detectives followed her into the petrol station, telling witnesses they were police officers.

Uniformed officers arrived at the station and tried to convince the two detectives to leave with them quietly.

The pair refused, so the senior sergeant from Papakura was called.

When the two detectives refused to go to the station with the higher-ranking officer, they were arrested.

The incident was captured on CCTV.

Police spokesman Kev Loughlin last night confirmed an officer will appear in the Papakura District Court on a charge of disorderly behaviour.

The other has not yet been charged.

The Independent Police Complaints Authority has begun an investigation into the incident.

Mr Loughlin would not comment on the incident, or discuss the officers' employment status.

"The issues around the incident have yet to be fully determined," he said.