The government now admits it's "essential" to use a new, wide-ranging test to assess the health impacts of firefighting foam contamination, but the test is not being used.
Hundreds, if not thousands, of households around the country are within zones bordering sites of confirmed or potential contamination.
RNZ reported last week that a standard testing method is being used, which is good for detecting the two banned chemicals PFOS and PFOA.
However, a new test called a TOP assay or TOPA could also be used to find hundreds of similar long-lasting and harmful chemicals in the water or soil, which would otherwise go undetected.
The Environment Ministry last week said the standard testing was good enough, but a new statement from the all-of-government group set up to run the nationwide foam investigation contradicted that.
"TOP Assays are valuable and provide summary level information about PFAS compounds in soil or water. They are essential in planning for long-term site remediation or for assessment of longer term potential health effects," it said.
Scroll to end of article to read the full statement
A spokesperson refused RNZ's request for an interview to explain why this essential test was not being used, saying the statement was all that needed to be said.
"TOP Assays do not add to Defence's ability to identify households at risk and therefore Defence is not currently using those assessment methods," the statement said.
Defence had also not used them during the two-and-a-half years it was testing groundwater in secret near contaminated air bases in Manawatū, Marlborough and Auckland.
If the foam investigation moved into a clean-up phase, the new test would have to be used, the all-government group said.
Regional councils nationwide had been told to identify at-risk sites from contamination by the wider class of PFAS chemicals by the end of March. It is unclear if they have done so.
Clean-up has proved extremely difficult and expensive overseas, so the preferred approach is to stop the chemicals getting out in the first place.
A Queensland environmental medicine specialist, Andrew Jeremijenko, compared New Zealand's water testing approach to his own government's approach to blood testing around Australia's many contaminated zones.
"I've heard from residents that they had to fight very hard to get those blood tests, and then once they've had them done ... it has been difficult to get those results and difficult for the government to give you the interpretation of those results because the government doesn't want to admit to the health effects," Dr Jeremijenko said.
Australia has recently put more than $20m into a foam response including counselling services and an epidemiological study across three badly-hit towns.
Dr Jeremijenko has made a submission to Australia's Expert Health Panel for PFAS, arguing for more explicit health advice about the associations of PFAS exposure with thyroid conditions, cancer, immunology and the like.
Australia is now making changes, such as advertising free blood tests in contamination zones.
It had about a two-years head start on New Zealand, but both countries' Defence Forces were continuing to express resistance to using the TOP Assay tests.
In the US, large numbers of military sites admitted to large scale contamination or were being investigated.
Its Centres for Disease Control was designing a $13m nationwide research project into the health impacts of PFAS, while the National Institute for Occupation Safety and Health was already conducting multiple studies of firefighters, including measuring their blood during training to use the foam to fight fires.
However, in New Zealand, the government recommended people not get blood tests, saying there was "no conclusive evidence that PFOS and PFOA exposure will result in future health problems.
It did allow for GPs to send someone for a blood test for "peace of mind" if the GP thought in necessary.
Auckland lawyer Tim Gunn said New Zealand was out of step with Europe: limiting blood testing, not using all the water testing available, and not testing enough other materials like soil.
His firm Shine is suing the military in Australia over foam contamination.
"NZDF have chosen to keep this matter secret since early 2015 - they have not told government, local or regional council until the media have become involved," Mr Gunn said.
"Limiting the testing to groundwater only and screening for a limited number of the known compounds is not consistent with the precautionary principle.
"Furthermore, the decision to not publish the testing results puts them at odds with the approach being adopted by the Australian Defence Force. This leads to the assumption that NZDF are trying to manage the release of testing results as a means to protect their interests."
Defence has told RNZ it has tested only "a small number" of soil samples for PFAS compounds.
"They should be pushing for testing of surface water/overland flow, and the general biota," Joshua Aylward of Shine in Australia said.
"The NZDF testing reports, whilst they test for more than PFOS, PFOA and PFHxS, they need to make sure they're testing for as many of these ... [PFAS] chemicals as they can, because the current science is that ... they're really all as bad as each other."
Statement from all-of-government PFAS programme spokesperson: