The organisation, which includes New Zealand's biggest news website and daily newspapers in Wellington and Christchurch, tasked 20 journalists with investigating its own journalism.

After several months, Stuff found its outlets had "been racist, contributed to stigma, marginalisation and stereotypes against Maori".

On the front page of its newspapers and on its website is a banner headline: "No matou te he" or "We are sorry".

"Our monocultural lens means we haven't always fairly represented tangata whenua (people of the land)," the editorial reads.

"We apologise to Maori."

Prime Minister Jacinda Ardern welcomed the initiative, saying "good on them".

"It's only a healthy thing for - be it government or be it the fourth estate - to constantly look at our role and place (on) some of the debates around social cohesion," she said.

Stuff's investigation began in June, following a management buyout from previous Australian owners Nine, which inherited the Kiwi company when it merged with Fairfax Media in 2018.

Project lead Carmen Parahi said the company "wanted and needed to be pushed harder to be better, to be more representative of all people in New Zealand".

"Our experience of the settler media is it supports settler interests. And that would be the same in Australia.

"I would challenge Australian media to do better for indigenous peoples."

Editorial director Mark Stevens noted the historical nature of some of the reporting, including references to an "inferior race" back in the 1800s.

The investigation found Stuff's reporting marginalised Maori to the present day.

"Our language often split New Zealand into two - Kiwis and Maori. Two separate groups, us and them," Mr Stevens said.

"Take the Foreshore and Seabed Act debate ... 'Debate over Maori customary rights to the foreshore and seabed is making New Zealanders nervous'."

Chief executive Sinead Boucher said it was imperative the company reckoned with its history in order "to be a trusted partner for tangata whenua (people of the land) for generations to come".

"If you think the job of the news media, in our company and others, is to hold the political to account, well, we are the powerful," she said.

"I think it is only fitting that a progressive company can pause and have a look at itself."

As part of its response, Stuff has launched a new charter, which will ensure journalists receive cultural and language training.

The company has also pledged a second part to the investigation in 2021, which will "focus on Aotearoa and how our racist past has made us who we are today".

Stuff has also begun to translate its stories into te reo Maori, the Indigenous language.

Australian Associated Press