Figures released by a major meth-testing company have laid bare the scourge of P contamination in New Zealand rental homes.

Data collected by MethSolutions showed that of 8845 homes it had checked for methamphetamine contamination in the past four years, 40 per cent had tested positive.

That rate was seen across Auckland, Bay of Plenty, Northland and Waikato - and even higher in Coromandel, where 49 per cent of homes visited tested positive.

Figures were higher in the North Island than in the South Island, where the rate was around 30 per cent, and there had been no difference in long-term trend, said company director Miles Stratford.


In Auckland, positive test rates were particularly high in Waitakere - 363 of 798 homes were found to be contaminated - as well as in Papakura and Waiheke.

"Each month more rental properties are being tested for meth and it saddens me that the rate is not dropping," Stratford said.

"This shows that the extent of the problem is widespread and the public is only just becoming aware of the need to protect their investment assets from tenant abuse."

Stratford said there was no reason to suggest a bias in the figures toward homes being tested because of suspicion; rather, it was becoming a norm for homes to be checked before sale or for insurance purposes.

"So it's not like people are phoning us because they've seen this or that, or that there's a risk with the property - it's simply the fact that it used to be a rental."

Other meth-testing companies have similarly reported high rates of positive results.

"This year, the general public has just become more aware about the issue," Meth Check NZ director Hayley Wilson said.

The figures also weren't surprising to property groups.


"This is an indication of the extent to which homes are being affected, and of course, bringing about losses that will result in the owners suffering financially," Home Owners and Buyers Association president John Gray said.

Clean-up costs ranged from $1000 to hundreds of thousands of dollars, with hefty replacement costs for furnishings, curtains and wall coverings.

"We have to look at the nature of the problem, and in this point in time, it's open-ended. How long will it go on?

"That is a matter for the Minister of Police to answer really, because it's about stamping this problem out."

New Zealand Property Investors Federation president Terry le Grove said it was now common knowledge the country had a major P problem that was now affecting many homes.

Ministry of Health guidelines say any 10sq cm area with a P concentration of 0.5 micrograms or above is not safe and readings in the worst-case scenarios can hit thousands of micrograms.

Recent figures from Housing NZ, which spends millions of dollars each year on remedial work and testing, showed 688 of 1266 properties tested had results that exceeded the Ministry guidelines.

But Dr Nick Kim, a senior lecturer in environmental chemistry at Massey University, said that in homes where P had only been smoked, it was rare to find levels that would constitute a health risk.

Methamphetamine contamination guidelines were being developed by Standards New Zealand and were expected to be complete next year.