Waikato River co-negotiator and respected Tainui figure Lady Raiha Mahuta has died.

Lady Raiha, who had been ill with cancer and suffered a heart attack last year, passed away early this morning aged 67.

Lady Raiha and Tukuroirangi Morgan, who leads Tainui's executive board Te Arataura, negotiated with the Crown on behalf of Waikato-Tainui in 2008 signing a settlement deed with the Labour government which guaranteed it a $210 million fund to clean up the polluted Waikato River, and a river co-management deal between itself and the Crown.

Mr Morgan said through a spokeswoman that Lady Raiha was to have attended today's Joint Management Agreement signing with The Waikato District Council at Ngaruawahia.

The agreement will allow the council to engage with Waikato-Tainui on matters of commonality, including the planning and regulation of the Waikato River.

Mr Morgan said Lady Raiha would have been happy to finish the job that her husband, the late Sir Robert Mahuta, started.

Maori Party co-leader and Maori Affairs Minister Pita Sharples also paid tribute to Lady Raiha, saying the Maori Party's thoughts were with her whanau.

"Lady Raiha stepped forward when her husband passed away - she saw the job through, despite her long illness, and only last weekend her people were able to salute her huge achievements.

"She commmanded great respect from the Crown in our dealings on Treaty matters, for her commitment to principle, tempered by the best interests of her iwi and the nation."

Labour Party leader Phil Goff also expressed sadness at Lady Raiha's death.

"I was informed by text in the early hours of this morning. My condolences go out to Nania and to all the Mahuta family. Lady Mahuta made a huge contribution to Maoridom. We mourn her loss it is premature. She had so much more to offer."

Green Party Co-Leader Metiria Turei said Lady Raiha's commitment to the environment was "an inspiration to us all".

"I would like to pay tribute to all the work she has done to protect the Waikato River for her people. She was a courageous negotiator on the Waikato River claim, and I know that she will be deeply missed."

Lady Raiha's body will today be taken to Turangawaewae marae, where she will lay in state briefly outside the house, Mahinaarangi.

She will then be taken to Tainui's endowed college at Hopuhopu to where Sir Robert is buried.

Her tangi will be held at Waahi Marae, Huntly, tomorrow and Thursday before she is taken to her home marae, Karetu, near Russell in the Far North on Friday morning for burial.

When the original Waikato River settlement deed was signed in 2008 beside the river's banks in Ngaruawahia, Lady Raiha's voice rang out in a traditional pao, a song where she traced the water's journey from Taupo to Port Waikato.

For the hundreds of Tainui people gathered it was a poignant moment as many reflected on the family's contribution to moving the tribe towards settlement - Lady Raiha's as well as that of Sir Robert Mahuta, who died in 2001.

- With NZPA