Potential new guidelines have been released by the Ministry of Health around what constitutes a methamphetamine-contaminated house.

LISTEN ABOVE: Peter Lewis, Auckland Property Investors Association vice president, spoke to Mike Hosking

They're based on a report it funded, that suggested the contamination levels that prompt a house clean-up should be four times higher in many cases, than they are currently.

They would raise the contamination reading from 0.5, to 2 micrograms per 100 square centimetres.

The Drug Foundation's Ross Bell says it's about time - because up until now the ridiculously low levels have created a sort of decontamination hysteria.

"We now have a testing industry who have scared the country into believing that the majority of state houses, the majority of private rental properties, have been contaminated by meth. That's not true."

Mr Bell said both private home-owners and the government have been throwing money away under these lower guidelines.

Housing New Zealand has spent $22 million on testing for P, and on clean up, so far this year - and most of that's been a waste, he said.

Property investors are welcoming possible new rules on what constitutes a methamphetamine-contaminated house.

Auckland Property Investors' Association vice president Peter Lewis is welcoming possible new rules on what constitutes a methamphetamine-contaminated house.

He said it makes sense.

He told Mike Hosking there's been great confusion between contamination caused by the manufacture of the drug, and that caused by the smoking of it.

"Because when you manufacture the product, as well as the P itself you've got all sorts of other nasties as well such as sulphuric acid and nitric acid."