The National Party is accusing the government of blocking the release of a report into the performance of the Māori Health Authority/Te Aka Whai Ora.
The review is described as a high level assessment of Te Aka Whai Ora's progress and was received by Health Minister Ayesha Verrall six weeks ago.
National Party health spokesperson Shane Reti said it included a review by consultants EY, and people in the sector had told him it raised some serious concerns.
He asked for a copy under the Official Information Act but the minister turned him down using a clause to protect the confidentiality of advice from officials to ministers.
Reti said that was not good enough.
"I think this needs some sunlight. I don't think the minister should be blocking or hiding this information," he said.
"New Zealanders deserve to know where their taxpayer dollars are being spent and if it is achieving anything. Claiming to be the most 'open and transparent' government ever and then hiding from accountability is hypocrisy."
Verrall said she would eventually release the report but needed more time to properly consider it.
Cabinet had commissioned the Hauora Māori Advisory Committee to look into the set up and progress of the Māori Health Authority, which was launched in July last year, she said.
The advisory group worked a similar way to the technical advisory groups during the Covid-19 pandemic - providing expert, independent advice to the government, she said
"It's standard practice when you have a large piece of work for the minister to have advisory committees to give you assurance on practice. That's what the public would expect us to do," Verrall said.
The minister would not say when the report would be released, only that it would be in "due course".
"We will take the time to digest it and to make sure we've made a clear view on what it says and how we want to approach it," she said.
Asked whether Reti was correct, that the report was critical, the minister said she had not "formed a full view" yet and that was why it was still under her active consideration.
"This is a report into a new health entity and so we need to make sure that those sorts of expected issues in a new entity get worked through," she said.
Reti said he doubted the report would be released soon, and that he was still waiting for a Covid-19 review from the minister from October.