Mr Tamati said he fully supported Dame Susan's stance.
"One of my four campaign pou or policies is calling for the government to launch a royal commission of inquiry into the abuse of children in state care.
"I back Dame Susan Devoy in her request to the UN to push our government into action."
Between the 1950s and 1990s more than 100,000 children and vulnerable adults were placed in state-run institutions, the vast majority of whom were Maori.
It is estimated up to 3.5 per cent of them suffered physical, sexual and mental abuse while in care.
Mr Tamati said child abuse was linked to high Maori imprisonment rates.
"I have seen first hand the links between child abuse and the high incarceration rates of our people."
Mr Tamati said working for a trust that pioneered a Maori rehabilitation programme gave him an insight into these links.
"Calling for a royal commission into the state abuse of children elevates this issue to a level of seriousness that it urgently needs."
Mr Tamati, a former New Plymouth district councillor and rugby league player, was chosen in October to run against incumbent Labour MP Adrian Rurawhe. Jack McDonald is standing for the Green Party in Te Tai Hauauru.