A loaded gun was left in a Parliamentary bathroom by a police staff member.
The Glock firearm was only retrieved after police were made aware it had been left in the bathroom and police are investigating the incident.
"Staff attended and recovered it from the occupant, and we would like to thank them for their assistance," Superintendent Chris Scahill, national manager response and operations, said in a statement.
"This was a regrettable incident that we are taking very seriously, and we acknowledge the potential risk that this could have posed."
Mr Scahill said police would not provide further comment while the matter was under investigation.
The Diplomatic Protection Service is a branch of police that has an office at Parliament, and is also responsible for the protection of the Prime Minister.
The incident occurred yesterday, which was a sitting day meaning MPs were at Parliament. Prime Minister John Key was in Auckland.