Countless homeowners have also forked out for pre-purchase meth tests or costly decontamination work that now appears to have been unnecessary.
In response, industry body the Real Estate Institute called for the watchdog to urgently clarify disclosure rules for agents, given P contamination was such an emotive issue for buyers, which also carried professional obligations for licensed agents.
REA chief executive Kevin Lampen-Smith issued a statement today saying real estate agents were not obligated to disclose confirmed results below 15 micrograms per 100cm2 unless they were asked.
"Methamphetamine contamination of 15 micrograms per 100cm2 or above will now be considered a property defect that must be disclosed to potential buyers."
Lampen-Smith said this position reflected the findings in the Gluckman report.
The report said that methamphetamine testing was only necessary if there was a strong suspicion or advice from police that a property had been used for heavy methamphetamine use or production using solvents or highly toxic chemicals.
"The REA welcomes the report, which brings much-needed clarity to an extremely fraught area.
"The chance of buying a house with risky levels of methamphetamine contamination is very low. It is highly unlikely that 40 per cent of New Zealand properties are contaminated as has been reported previously."
Lampen-Smith says people looking to buy property should visit settled.govt.nz to learn more, and always ask the real estate agent if they were concerned about methamphetamine contamination.
"We strongly encourage people to ask lots of questions when buying a property. If you are worried about potential methamphetamine contamination because you suspect the property was used as a meth lab, ask your lawyer to include a satisfactory meth test as a condition of your offer."
However Lampen-Smith said the new guidance and findings in the report did not alter previous disciplinary decisions made by the regulator's Complaints Assessment Committees or the Real Estate Agents Disciplinary Tribunal (READT).