The union for prison staff says they want officers to be able to carry pepper spray and not just to have it available at the prison.

Corrections Minister Anne Tolley announced on Tuesday that prison staff throughout the country will have access to pepper spray following a successful 12-month trial at 10 prisons around the country.

But she said they won't be allowed to carry it on their belts because there was a risk of prisoners assaulting staff and stealing the cans.

Ms Tolley said in a statement that this was supported by prison managers and staff.

But Corrections Association president Beven Hanlon says the staff actually want to carry pepper spray in high security, maximum security and management units, where assaults took place on a regular basis.

"We think we need some sort of deterrent to stop these assaults, and we think that carrying pepper spray on the hip would be the place to do it," he told Radio New Zealand.

Mr Hanlon said the association represented more than 2500 of the 3000-odd corrections officers and that the issue was discussed as they were ratifying their collective contract.

"Not on person spoke against what we were trying to achieve for officer safety."

He said the risk of being seriously injured by pepper spray from an inmate was less than being stabbed by a knife and fork supplied to an inmate with a meal or being hit by a 2kg radio they carried.

However, he said Tuesday's decision was a step in the right direction.

Public Service Association (PSA) national secretary Richard Wagstaff says making pepper spray available would help keep staff safe.

"It's important to remember that it can only be used as an option during a planned force situation and that is very appropriate for the New Zealand prison environment. We would not expect to see it used regularly."