The Independent Police Complaints Commission is investigating alleged misuse of a police computer system that led to the release of information.
The IPCC, the body that has overall responsibility for the police complaints system, is probing allegations that a police officer misused the North Wales Police computer.
The officer has been arrested and released on police bail and is suspended from duty while the investigation is carried out.
IPCC commissioner Tom Davies said: "Very serious allegations have been made against a serving police officer. I have decided the investigation needs independent oversight and this will be managed on my behalf by an IPCC investigator."
The IPCC would not comment further on the case because of potential legal proceedings.