A group which represents landlords is annoyed property managers are dropping clients whose properties haven't been insulated.
From Monday, rentals will legally be required to have floor and ceiling insulation where possible. The Ministry of Business, Innovation and Employment estimates there could be 100,000 properties that don't comply.
Landlords face potential fines of up to $4000.
Property Investors' Federation (PIF) chief executive Andrew King told RNZ property managers have cut ties with landlords who haven't insulated, because they too could be fined.
"Some property managers, hopefully the majority, have been very professional and got onto this early and actually provided good information to their customers and their clients," he said.
"Others haven't, and in fact have left it to the owners of the rental property to actually do that work for them."
He's heard some members of the PIF have been dumped by their property managers on realising there was no insulation.
"It's... fair to say that some of these landlords assumed that the property manager was actually managing the property for them and should have actually told them what the regulations were and if they in fact met them," he told RNZ.
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Last week King told Newshub tenants shouldn't be afraid to dob in landlords that don't get their properties up to scratch, and shouldn't fear being evicted.
"If [landlords]... end the tenancy because they're complaining about the lack of insulation, they can be held accountable for that - and that's another $4000 in exemplary damages. So there's a lot of costs in not doing what you're meant to do."
He said some tenants requested delays on getting insulation installed to stave off rent increases, but some landlords have left it too late.
"I hope there is some leeway towards them," he told RNZ.
The Ministry of Business, Innovation and Employment said in May there would be no mercy "as this would be unfair to those landlords who have acted in time to do the right thing".