The Green Party says landlords who don't keep their homes up to scratch should be banned from renting them out.
The party has renewed its call for a rental warrant of fitness, saying standards need to be enforced.
"It's all good and well having minimum standards," co-leader Marama Davidson told Newshub Nation on Saturday.
"What we need for that to work is actually having put in place an enforcement regime to make sure that we've got people who can rent houses without having to have the burden of making complaints for damp, mouldy, cold homes or homes that are in disrepair, which is what happens at the moment.
"A lot of that burden is on tenants, and that's a high threshold to be able to get some action."
She said rather than having to take bad landlords to the Tenancy Tribunal, renters should have confidence their property is safe and will be kept that way.
"Right at the get-go people even looking for a home should be assured, in this country, that your home to rent will be up to a certain standard… if a home cannot pass the standard, it cannot be rented out."
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She couldn't tell host Lisa Owen what an enforcement regime would cost.
"But it costs us to have unhealthy homes - for example, over 40,000 admissions to children's hospitals over the winter just from homes that are in bad condition and are unsafe, unwarm, drafty and mouldy."
The Government last year passed its Healthy Homes Guarantee Bill, which will set minimum standards for rental properties.
The Greens have been pushing for a rental warrant of fitness for years.
"National’s refusal to adopt comprehensive minimum standards, beyond the paltry insulation and smoke alarm provisions they've offered up, will mean more Kiwis living in rotting, mouldy homes, and more children getting sick or dying because of it," former co-leader Metiria Turei said in 2015.