All state houses may be tested for methamphetamine contamination when they become vacant, after a huge jump in affected houses in two years.

Housing NZ says it found only 28 meth-contaminated state homes in the year to June 2014, but 229 in the year to June 2015 and 279 in the second half of the year.

Chief operating officer Paul Commons said testing all state houses upon vacancy was "under consideration as we constantly review our procedures". But a decision will not be made quickly as the agency has only recently changed its focus from looking for P labs, where houses were used to make the drug, to testing homes where anyone was suspected of using it.

Auckland regional manager Diane Te Nana said the agency had a zero-tolerance approach to methamphetamine.


"If we have suspicion, we test, and that will be a reason for ending the tenancy," a spokesman said.

The jump in the number of contaminated houses appears to be largely due to increased testing, although there are some signs Kiwis' use of the drug may be rising again.

Health Ministry surveys found meth use peaked at 2.7 per cent of the population in 2003, declining to 2.2 per cent in 2007-08 and around 1 per cent in each of the past four surveys from 2011-12 to 2014-15.

Dr Chris Wilkins of Massey University, who surveys illicit drug users annually, said his latest survey, due out next month, would show some signs of increased use.

"Overall the levels of methamphetamine seem to be fairly stable, but we have found consistent increases in availability in Christchurch over the last 18 months or so."

Forensic scientist Dr Nick Powell said any meth contamination above 0.5mcg per 100sq m of surface risked headaches, coughs and sleeplessness, and poorer appetite and infant brain growth.

He has found traces of the drug in half of the many motel rooms he has visited in the North Island and Australia and in a third of motels where he has slept in the South Island.

Housing NZ said it cost about $2750 to test for the drug, $10,000 to clean up and $1600 to test for an all-clear.

Contaminated state houses

Year to June 2014: 28

Year to June 2015: 229

Half-year to Dec 2015: 279