The Corrections Minister has hit back at National's claims of wasteful spending on prison slushy machines, saying he won't apologise for looking after staff.

Photo: Michèle Constantini / Altopress

In response to an Official Information Act request by the party, Corrections has revealed it bought 193 slushy ice machines for prison staff over summer.

National leader Simon Bridges is criticising the million-dollar bill and said the Corrections Minister, Kelvin Davis, needed to explain and apologise.

"This is extravagant, wasteful spending. They managed the year before without 193 slushy machines at over a million dollars and they could have this year as well. I think taxpayers will see it as a real extravagance."

Mr Davis said spending was an operational matter but he supported measures that improved staff's safety and well-being.

Photo: RNZ / Richard Tindiller

"Staff work hard managing some of society's toughest people. When you've got Corrections officers working in extreme heat and wearing 6kg stab-proof vests, it's vital they are able to keep cool, safe and healthy - and that helps ensure they're able to do their job well too.

"It's a disgrace that Simon Bridges is trying to politicise staff health and safety. This is nothing like the last National Government spending $26 million on a flag referendum or hundreds of thousands on a single TV screen, reception desk and hair straighteners. This is about looking after our people and making sure they're able to perform well - and I make no apologies for it."

The department's acting national commissioner, Andy Milne, said the hot summer of 2017-18 caused staff significant discomfort and risked raising prisoner tension.

He said Corrections provided staff with cold water, hand-held fans and cold flannels, and it bought the slushy machines before this summer to keep them cool and avoid dehydration.

Mr Milne said the machines were more effective than drinking water.

Twenty-six of them were placed in Rimutaka Prison, and 20 in Mt Eden.

Photo: RNZ Insight/Philippa Tolley

Corrections' chief custodial officer, Neil Beales, said it was the department's job to support staff safety and the one-off purchase would be available for many summers to come.

The vice-president of the Corrections Association, Paul Dennehy, said the slushies were one of a number of recommendations they put to the department in an attempt to alleviate staff discomfort in trying conditions.

"When the temperatures get high and staff are working in close proximity to prisoners however good the air conditioning may be in a residential unit it's difficult and demanding circumstances our staff are working in.

Staff were often working long stints and wearing heavy vests for their protection.

"I think anyone at all, when the temperature rises tempers fray a little bit. You put that in an environment such as we work in then the conditions we work in and the dangers we face are exacerbated.

"I think it has been a success because it's just one element we can have to make our staff's working day slightly more bearable. We're dealing with the most violent people in society, this is just one of the range of tools.

Concerns about tackling the heat had been around for some time and he was disappointed National had raised issue with it, he said.

"I understand Mr Bridges and the need for financial and fiscal prudence and the question to be asked, it's just disappointing that he's come out so anti it when his party when they were in power introduced measures to alleviate the heat temperatures that prisoners were feeling by giving them iceblocks and icecreams, bottled water, and fans whilst at the same time providing staff with nothing."