The Ombudsman's office has ordered the Ministry of Health to release previously confidential data from dioxin blood tests on New Plymouth residents.
Campaigners for people who lived near the Ivon Watkins Dow chemical factory at Paritutu while it made the herbicide 245T have been asking for individual blood-test data for over a year. The ministry has refused.
However, director of public health Mark Jacobs told National Radio it must now reveal the dioxin levels found in each of the 52 people tested.
"The issue has been one of confidentiality and the ethical approval ESR got to do then study in the first place," he said.
"Obviously the ombudsman was in a position to balance all of those things and make a judgement at the end of the day."
Forensic accountant John Leonard, who claimed the ministry's blood study was flawed, said the fresh data was not sufficient to prove the extent of the dioxin problem.
Mr Leonard had earlier said he believed high levels of dioxin contamination at the plant were obscured by poor methodology in last year's Ministry of Health report.
Tests have found people who lived near the factory had up to seven times more dioxin in their blood than other New Zealanders.
The ministry has admitted dioxin causes four rare cancers.
On Monday, the ministry said it would ask for an additional expert to independently review its report, after critics questioned the independence of ministry appointed scientist Professor Allan Smith -- a scientist at the University of California at Berkeley.
Deputy Director General of Health (Public Health) Dr Don Matheson said the ministry would approach the World Health Organisation (WHO) to seek advice about appointing the additional reviewer.