Associate Health Minister Tariana Turia says there is "institutional racism" in hospitals.
New research suggests a disparity between Maori and non-Maori healthcare.
An Otago University study published in the New Zealand Medical Journal says a review of literature has shown that Maori receive poorer in-hospital treatment according to current standards and clinical need.
Obstetrics, cardiac intervention, end-stage renal disease and mental illness are areas with particular disparities.
Mrs Turia says the findings are unacceptable and she is calling on hospital hierarchies to raise the bar on the care provided to Maori.
Listen to full Tariana Turia interview
DHBs aware that Maori disadvantaged
District Health Boards say they are already aware that their service needs to improve for Maori.
The chair of District Health Boards New Zealand, Peter Glensor, says he accepts different health outcomes exist between Maori and non-Maori patients.
But he says that is not new information and DHBs are working to close the gap.
"That's something we know to be true and it's something that we have a strong commitment as District Health Boards to make sure that our public hospitals are providing top quality care to every New Zealander."
Mr Glensor says he has already extended an invitation to discuss the health system with Mrs Turia.