Ministry of Health says it will not be sharing Māori vaccination data with Whānau Ora Commissioning Agency (WOCA) at the scale the agency wants.
The agency has been seeking contact details for all unvaccinated Māori in the North Island so it can target areas with low uptake, when it embarks on a vaccination drive.
The ministry has declined to provide those details, despite being told by the High Court on Monday to re-consider.
The agency's chief executive John Tamihere said the ministry's Director-General of Health Ashley Bloomfield has now decided to stand by its decision, right as 70 staff launch a vaccination drive in Tai Tokerau.
"The problem with Mr Bloomfield doing this is that we're going on a fishing expedition into uncharted sea and it's unfair. If we knew where we could direct all our resource we will lift Māori vaccination rates - there's no doubt about it."
Tamihere said the agency must have immediate access to the data so "we can give our people an opportunity to be vaccinated and a chance".
The ministry wants to work in partnership with the agency, instead of providing the data, he said.
In a statement, Bloomfield said the ministry had taken into account the views of Māori health experts, representatives and iwi leaders, and "making good decisions to support and protect whānau was highlighted as most important in this consultation".
"While WOCA's proposed use of the information, given its breadth, would be effective to address the risks associated with Covid-19 in some regions, the ministry's view is that it would not be effective in other areas, due to variations in WOCA coverage, and the role and approaches of other providers," Bloomfield said.
However, he said the ministry was still open to sharing some data where appropriate.
"The ministry has proposed a way forward that would open the door for further sharing of personal health information of individual Māori in specific locations, with WOCA," Bloomfield said.