Green Party co-leader Marama Davidson says landlords should be required by law to ensure the homes they rent are fit to live in.
Under a proposed warrant of fitness scheme, rentals would have to be approved by independent inspectors to ensure they were warm, dry, and healthy.
Ms Davidson said that if a home did not meet basic health standards, it ought not to have been rented.
"There should be no home for rent in New Zealand that is not up to standard," she said.
"So making sure it is warm, dry, ventilated ... and making sure it can be easily heated."
That included having a minimum warmth rating of 18 degrees Celsius, Ms Davidson said.
Homes would also have to be fully plumbed, and be equipped with "basic facilities".
Ms Davidson said that while most landlords understood these necessities needed to be met, some just did not care.
"Those landlords that are actually exploiting people for rent and renting out unsafe and unfit homes ... there needs to be standards and there needs to be an enforcement of bringing those homes up to scratch," she said.
"And so at the moment, we know that this isn't always happening."
Ms Davidson said it was disgraceful that more than 40,000 children were admitted to hospital each winter because their homes were not properly warm and dry.
But not everyone is on board with the idea.
National Party spokesperson for housing and urban development, Judith Collins, said the scheme was "another of Marama Davidson's crazy ideas."
She said the WOF programme would render more people homeless and that it completely ignored New Zealand's current shortage of rental accommodation.
"We have this year the largest number of families - around 8500 up to 9000 on Housing New Zealand's waiting list. We need more rental accommodation not fewer," she said.
"We have more people, according to the minister, who are living in motels, and we need to actually have people in houses."
Ms Collins said many inappropriate homes, such as the Papakura swamp house were already in breach of the law as it stood, so there was no need to further regulate the rental market.
"We don't say for instance that because somebody breaks the law when they're drunk driving that the law's not right," she said.
"We actually say that they're breaking the law anyway and we take action."
Ms Collins warned that Ms Davidson needed to think twice before closing some landlords out of the rental market.
"She needs somewhere for people to go and stay."