The policeman who left a loaded gun in a bathroom in Parliament was a trusted officer who made a "catastrophic mistake," Prime Minister John Key says.
He revealed today the officer was a member of his protection squad, and had been on the team the whole time he had been Prime Minister.
"He is utterly professional, I trust him implicitly," Mr Key said.
"He just made a catastrophic error, it's pretty awful for him because he's not that kind of guy, he doesn't make mistakes easily."
The Glock firearm was found in the bathroom on Thursday, and was retrieved as soon as police were told it was there by whoever found it.
Superintendent Chris Scahill, national manager response and operations, said at the time it was "a regrettable incident" and he acknowledged the potential risk that it posed.
A police investigation is under way, and Mr Key said he couldn't say much because of that.
Asked if he would provide a character reference for the officer, Mr Key said he would if requested.
"Unfortunately, sometimes these things happen," Mr Key told reporters.
"I know it makes a terrible headline and he will be beating himself up enormously, but he just genuinely made an error and the police with deal with it."