KIWI inmates are being told to swap cigarettes for carrot sticks before they are forced to kick their tobacco habit altogether.

New Zealand jails will go completely smoke-free in July as part of radical new laws designed to make prisons safer and healthier.

To prepare addicted prisoners in the lead-up, the Department of Corrections is trialling a bizarre national directive to supply inmates with two carrot sticks a day.

A memo leaked to the Southland Times provides costings, stating that one jumbo carrot provides 16 carrot sticks which are to be cut into uniform sizes "to the best of our ability".

It suggests a good way of distributing the carrots is by reusing bread bags, the newspaper reported.

Corrections Association of New Zealand president Beven Hanlon has admitted that when he first heard about the "alternative therapy" he thought it was a joke.

"I don't think it is one of (the department's) best ideas but it is worth a try," he said.

Mr Hanlon doubted it would last but said at least it was healthier than handing out lollies.

"It's the whole oral thing... if they have got something in their mouth, they won't be looking for a cigarette to put in it."

New Zealand prisons stopped selling cigarettes last week and, as of July 1, all tobacco products will become nationally prohibited items, or contraband.

Most of the country's 5700 smoking prisoners have been using nicotine patches for the past year in preparation for the move.

The ban, announced last June, has been hotly debated, with many believing it curbs prisoners' civil rights, takes away their only pleasure and will increase the risk of rioting and violence.

Advocates, however, say evidence from a smoke-free British prison show violence decreased dramatically.

Without lighters, fire risk would also drop, and staff and non-smoking prisoners would no longer be exposed to dangerous secondhand smoke.

One New Zealand mayor has even suggested the prospect of serving time without being able to smoke would be an effective deterrent for many criminals.

When announcing the ban last June, Corrections Minister Judith Collins also made clear that the punishment nature of prison also played a role.

"We don't supply alcohol to prisoners because they are alcoholics, we don't supply them with all sorts of drugs and methamphetamine because they happen to be addicted to methamphetamine," Ms Collins said.

"This is a prison. It's not home. It's actually a prison. So it will be a total ban across all prisons. Not in the cells, not even out in the yard."

Originally published as Carrots, not cigarettes, for Kiwi inmates