Housing New Zealand has lost two recent cases in the Tenancy Tribunal over its attempt to pass methamphetamine-related clean-up costs on to tenants.
Last week, RNZ investigated the methamphetamine testing Housing New Zealand has been carrying out on state houses.
Tests that find tiny traces of the drug have been used to evict tenants who have then been banned from state houses and in some cases have had to pay tens of thousands of dollars in clean-up costs.
But a leading scientist and the New Zealand Drug Foundation say the tests are not fit for purpose and that Housing New Zealand is going too far in kicking out tenants on the back of the test results.
Housing New Zealand has also conceded the guidelines it uses to evict tenants are not suitable.
Nevertheless, last week its chemical contamination manager Charlie Mitchell defended the ongoing evictions and the agency's zero tolerance stance saying it was working on developing "more appropriate" guidelines.
Two recent Tenancy Tribunal decisions related to meth testing have gone against the agency.
In one case, a tiny level of meth, just above the guideline, was detected on an extractor fan in a house.
Housing New Zealand evicted the tenant and tried to charge them $10,000 for the clean-up in which doors were removed as well as an oven, extractor fan, and light fittings.
In July this year the tribunal ruled the decontamination work bore no resemblance to the contamination.
"This quote and outline of work has obviously been accepted at face value by HNZ without further enquiry or analysis," the tribunal ruled.
In another case, ruled on in May, Housing New Zealand tried to evict a tenant for meth contamination and fine them large sums - again after low levels of meth were detected.
In this case the tenant disputed the allegation and accused Housing New Zealand of breaching health and safety legislation by renting them an uninhabitable house.
Housing New Zealand had to refund several months rent to the man it had accused.
The Tenancy Tribunal decision found there was no way of determining when the contamination occurred.
Housing New Zealand Minister Bill English last week admitted to Morning Report the tests being used to evict tenants were not fit for purpose.
"No (they're not), and Housing New Zealand have said that," Mr English said.
"They're operating to a Ministry of Health guideline which is internationally standard but it's regarded as not quite appropriate for dealing with use of P in houses."
Drug Foundation executive director Ross Bell said Housing New Zealand was being heartless and called on Mr English to intervene.
"I think they're out of control, Housing New Zealand has admitted these tests are flawed yet they're sticking with their zero-tolerance policy and I don't know how they can justify that.
"Housing New Zealand has spent over $20 million in the last financial year doing these tests and these clean-ups knowing these tests are flawed. The minister should step in and stop the taxpayers' money being wasted and vulnerable people being punished."