Cuts to police training have left some officers facing potentially life-threatening situations without access to firearms, the Police Association says.
A new training regime appearing around the country places staff into categories, based on how likely they are to need firearms, it says.
Under current police rules, frontline police officers must have 24 hours of firearms training per year.
Youth Aid staff, who would receive no training under the changes, were among the first to arrive at the Napier siege, association president Greg O'Connor says.
A senior officer was killed and two other officers and a civilian were seriously wounded in the attack in May.
"You never know when you are going to be required to take up arms to assist your fellow officers," Mr O'Connor says.
The union says some traffic police in Auckland are already on duty without firearms training, even though they're often first at dangerous situations.
But Police Assistant Commissioner Operations Viv Rickard says no changes to training have been introduced in Auckland.
Mr Rickard told Morning Report the changes are not a cost cutting measure. Instead, the aim is to train staff who will be dealing with firearm incidents rather than those in back office jobs.
He says the use of tasers is providing an opportunity to look more widely into firearms training, though this doesn't mean those who might previously have been trained to use firearms will be given taser training.
He says staff that are more likely to deal with armed incidents should be given more firearms training.
According the union, one in seven officers have been threatened with guns in the past year.
The Labour Party says all police officers deserve firearms training.
Police Minister Judith Collins says the Government says it did not instigate the police review. She told Morning Report it is up to the Police Commisioner to make choices about how police use their budget for operational training.