Those behind bars at Christchurch Men's Prison say temperatures in their cells last week reached 40 degrees.
While the prison is now working to resolve heat related issues, it's promoted a discussion around the rights of prisoners.
Howard League, a group that advocates for prisoners' rights, advocate Kathryn Daley said it's just not good enough.
"It's a human rights issue, we need to know all New Zealanders are treated safely and humanely," Ms Daley told TVNZ1's Breakfast today.
They do not have air conditioning in their cells, she said and described conditions as "incredibly hot".
She said we need to start changing some of the attitudes around prisoners and their rights.
"We need to start joining together as a community and saying we want to see all New Zealanders being treated with dignity and respect."
"It's supposed to be about rehabilitation and reintegration," she said.
"The loss of liberty is the punishment, not to be subject to cruel and torturous conditions."
She said there are some units coping better with the heat, particularly those units with grass which Ms Daley says "make a massive difference".
But prisoners in units that have tarmac are suffering due to the heat.
"It needs to be thoroughly investigated," says Ms Daley.
Christchurch Men's Prison has been contacted for comment by 1 NEWS.
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