Across the three complaints, the inquiry found police were not justified in photographing the rangatahi and officers had not sought consent from the rangatahi themselves or their parents or caregivers.
RNZ reported of the tens of thousands of photos held in just one police database, half were of Māori.
The 135-page report said the rangatahi and their whānau who were interviewed as part of the joint inquiry had consistently raised concerns that their treatment was because of their race.
Coster said certain police training and processes could be improved. Whether a photo was appropriate depended on the circumstances but it would be required in some situations, he said.
"Photographs are an absolutely core part of the way we do our business these days so we have to be able to take them in some situations."
Coster said the organisation was examining the report, including understanding its implications.
"There's a real risk that the implication of this is that we will struggle to prevent some crime and to investigate crime and we need to get the balance right."
As RNZ reported earlier today, the report revealed a "widespread practice" had developed of officers routinely taking photographs of young people and adults in public for later identifications with little cause.
People were photographed for simply looking "out of place" or "suspicious".
Thousands of photographs of members of the public have been kept on officers' phones or transferred to the police computer system, which legally should be destroyed.
Coster said today "thousands" had since been deleted but he was unable to provide a specific figure.
In 2020, police in Wairarapa admitted to unlawfully taking photos of youths following multiple reports of officers stopping and photographing young Māori on the street.
RNZ reported how whānau describe their sons walking alone in broad daylight, when police have approached and insisted they take their picture.
One mother told RNZ her 15-year-old son was walking back to her place from his dad's house "minding his own business" when he was approached by police and his photo was taken.