Whānau Ora is heading back to court after the Ministry of Health refused to release data relating to unvaccinated Māori.
The ministry's stance is despite a High Court ruling on November 1 which said the Government's health agency should reconsider withholding the information.
Instead of handing the data over, the ministry has invited Whānau Ora to work in partnership with it, along with relevant iwi and local service providers, to identify areas where vaccination for Māori is most needed and what data sharing is "necessary and appropriate".
Whānau Ora took legal action against the ministry for refusing to release data on people who had not been vaccinated.
It asked the ministry to provide contact details of all unvaccinated Māori in the North Island.
The outcome of the High Court hearing was released on Monday last week, ruling against the ministry and asking for it to reconsider its decision to withhold.
The ministry asked Whānau Ora for a 24-hour extension on Thursday, to review its position.
But on Friday night, the director-general of health, Dr Ashley Bloomfield, contacted the agency to say the ministry had reviewed its earlier decision and would not be releasing the information.
Whānau Ora chief executive John Tamihere said it was disappointing and his organisation would now have to go back to court to try to get the ministry to release the data.
He said his agency would rather spend its time and resources on the vaccine rollout than a protracted legal battle.
"But we're obliged to go back to court because the Ministry of Health will block us from getting the data for vaccinating the under 12s and the booster shots."
Tamihere said the fact such a large number of Māori are under 12 means it has to happen.
"We've sent a letter to the Ministry of Health and we've said we're willing to work with it on this, but it hasn't come back to us yet - it's incredible. In the middle of a pandemic like this we need that data," he said.
"If we had it in September the vaccination rate for Māori would be right up there, it would be comparable."
Tamihere said it will be able to use the ministry data to text and email Māori who are unvaccinated.
Then individual Whānau Ora providers, like Turuki Healthcare in South Auckland, would be able to target specific streets identified as having large numbers of unvaccinated people with leaflet drops and vaccinations.
In a letter to Tamihere, Bloomfield said the ministry had considered the evidence provided by the Whānau Ora Commissioning Agency, as well as the views of Māori leaders and health experts.
"These views have demonstrated that there are multiple interests at play in the provision of individual identifiable Māori health data," Bloomfield said.
"In seeking to ascertain the Māori rights and interests that could be impacted by the disclosure of information for the entirety of Te Ika a Maui, and in light of the evidence of vaccine uptake and coverage, we have concluded that it would not be appropriate to adopt a blanket approach to the sharing of the Māori health information you have requested on a North Island-wide basis."
The Ministry of Health has been approached for comment.