Whānau Ora chief executive John Tamihere says the agency has been "consistently blocked at every step" by bureaucrats while trying to work with Māori on getting their Covid-19 vaccinations.
Whānau Ora has been fighting to access Māori NHI information so vaccine providers can directly contact unvaccinated Māori.
After several court battles, at the weekend that information held by the Ministry of Health slowly started to be shared with Whānau Ora, with Tamihere receiving information for Māori in Auckland and Waikato.
It means they now have access to 52,000 unvaccinated Māori.
But despite the success, Tamihere on Wednesday morning told Breakfast, it came "extraordinarily late".
While naming Director-General of Health Dr Ashley Bloomfield specifically in his criticism, he said it wasn't a competition and that he wanted to work with the Ministry of Health but needed "a willing partner on the other side".
"We just can't have Mr Bloomfield and his friends consistently blocking us at every step," Tamihere said.
"The take-away story from this is we are very capable and able now and we're trying to break away from welfarism and over-reaching bureaucracy and this is just an example of it and a very difficult moment in time.
"Our teams are as tired as all other teams are, but we really have to go hard on this one because we've only been given the information to unvaccinated Māori and we're having to mine that tail in a very difficult moment in time.
"We're gonna go hell for leather before Christmas to try and get our vaccination numbers up."
Tamihere said it was frustrating to get to this point, though.
"We're enabled and contracted to deliver services in health, welfare, education and justice across many years over large communities in the Whānau Ora area, and to be consistently blocked and frustrated by bureaucrats that seem to know better but don't is now starting to get extraordinarily tough on us," he said.
The Ministry of Health, which has been contacted for reply to Tamihere's comments on Breakfast on Wednesday, has previously cited privacy concerns for why it withheld data.
But Tamihere threw out that excuse.
"It's never been about privacy because when you run tens of thousands of enrolled patients up and down your clinic systems you've demonstrated, when you're running massive welfare programmes, you've demonstrated the protocols around privacy," he said.
"The court found that that was a nonsense, the court also found that the allegation that we were no good and that we did not have capability - found that was a nonsense too."
Tamihere said they were back in court on Thursday arguing for information of under-12s, as well as information around booster vaccines.
"Because in failing us in this present rollout, they will fail on boosters as well and knowingly fail," he said.
In a statement, Director-General of Health Dr Ashley Bloomfield told 1News the ministry "has entered data-sharing agreements with the Whānau Ora Commissioning Agency to release Māori health data for Waikato and Tāmaki Makaurau, and this data has now been shared".
"We are now focused on working with WOCA on appropriate data-sharing arrangements for other regions, subject to further consultation, and have been in hui with iwi, WOCA and DHBs over the past two weeks. We remain committed to finding resolutions that work for as many groups as possible.
"The ministry has also offered to share mesh block level data, which is down to neighbourhood level for the whole of the North Island. This offer still stands."