New standards for methamphetamine contamination in houses will be pointless if the meth testing industry itself is not regulated, the government has been told.
Standards New Zealand expects to have new contamination guidelines ready in June and a law going through Parliament will make those standards enforceable before the Tenancy Tribunal.
But the Drug Foundation was concerned those doing the testing could not necessarily be trusted.
Housing New Zealand was widely criticised for evicting hundreds of people from homes where only tiny traces of methamphetamine were found.
It used Ministry of Health guidelines that only applied to meth labs and were not intended to monitor homes where the drug had been smoked.
There were also concerns that people were spending thousands of dollars needlessly decontaminating their houses.
Building and Housing Minister Nick Smith said the proposed legislation recognised meth contamination had become a significant problem that needed clearer direction.
"Right now there's huge uncertainty, for Housing New Zealand and in the 400,000 homes that are tenanted, about what is the safe level.
"That's why the development of those standards is important... This bill is important in the sense of giving those standards legal status."
But Drug Foundation executive director Ross Bell said there was no point in giving new testing guidelines legal status, if the people carrying out the tests were not regulated.
"We have an industry playing on people's fear, on hysteria around methamphetamine.
"This industry should have to meet certain standards and those standards should be set by government," he said.
"There needs to be much better training around how the tests are done, what tests are used, what lab does the analysis and how those results are read."
Mr Bell also had reservations about the science being used to develop the guidelines.
"New Zealand seems to be the only country that's going down this route."
Dr Smith was confident the standards would be robust.
"I'm satisfied that Standards New Zealand and the expert team is pulling out all stops to get that work finished as quickly as possible," he said.
It was important that both the way the tests were done, as well as the thresholds for determining whether a house was safe or not, were based on "the very best science", Dr Smith said.
Labour's housing spokesperson Phil Twyford said the guidelines would not last the distance if the government did not regulate the industry.
There was also evidence to suggest that fewer houses were being used to manufacture methamphetamine, he said.
"Police says there's much less meth-cooking going on in houses now - most of it is happening in remote locations and cars."