Key Points:

A diplomatic protection squad police officer once shot a hole in the side of an airborne plane carrying former Prime Minister Jim Bolger, it has been revealed.

The DPS guards the Prime Minister and Leader of the Opposition, usually keeping a low profile.

But the decision to completely surround incoming Prime Minister John Key on election night with a tight ring of officers has raised questions about its tactics.

In a discussion panel on Radio New Zealand this week, Mr Bolger's former chief press secretary Richard Griffin said some officers were extremely gung-ho and one had once shot a hole in the side of an airborne plane carrying the Prime Minister.

Asked about the incident yesterday, Mr Griffin said it had occurred on an Air Force VIP flight in the 1990s.

He said DPS officers were supposed to take their Glock pistols out and disarm them.

"In the process of taking his Glock out and disarming it, he managed to discharge it, in the air."

He said there was no loss of pressure in the cabin and the flight continued, despite "a bit of panic".

"No one was really quite sure what had happened."

Mr Griffin said Mr Bolger was "sanguine" about the incident. The officer was mortified, and was no longer with the police.