Early in his church career, Dr Kaa was the Anglican priest at Taupo and Porangahau (Hawkes Bay), and from 1977 to 1983, he was minister of the Auckland Anglican Maori Mission.
During this period, he was a member of the Waitangi Action Committee, and with fellow members such as Hone Harawira and Shane Jones, both now MPs, was a strong advocate of tino rangatiratanga.
Through his work with the World Council of Churches and the Christian Conference of Asia, Dr Kaa supported the anti-apartheid movement in South Africa and indigenous rights movements in other parts of the world.
Political parties yesterday expressed their sadness at Dr Kaa's death, with the Maori Party describing him as a living legend of our times.
"Aotearoa has lost a fierce advocate, a champion for our children, and a veteran activist for the wellbeing of our whanau," said co-leader Tariana Turia.
Social Development Minister Paula Bennett said she would remember him "as a leader who worked to ensure the wellbeing of Maori children and for his contribution to the experts forum that led to changes to better protect all NZ children".