Former Governor-General Sir Anand Satyanand is stepping down from his role as the chair of the Royal Commission into historical abuse in state care over the increased "scale of work".
The inquiry was announced in February last year by Prime Minister Jacinda Ardern, who said at the time it was a chance to make sure the same mistakes are not repeated.
The inquiry is looking into instances of abuse between 1950 to the end of 1999, and is due to release its first report in 2020.
Sir Anand, 75, said when the Terms of Reference of the inquiry were announced by the Government in November 2018, the scope of it was widened to include faith-based institutions and the "scale of the work" increased.
"Because of that and the fact that the 'set-up' and development phase of the inquiry is nearly complete, I have opted to step aside for a new chair who can lead the inquiry through to the completion of this important process," he said.
"It has been both heartening and heart-breaking for the commissioners and I to hear from survivors first-hand about their experiences of abuse," he said.
"Sharing your experience takes courage and determination and I have admiration and respect for the survivors we've heard from for their bravery."
Sir Anand will leave the Royal Commission in November following the first public contextual hearing where commissioners will hear evidence from expert witnesses.
The Government will appoint a new Chair of the Abuse in Care Inquiry by November.
Sir Anand has been appointed Chancellor of the University of Waikato for a part-time governance and ceremonial role over a 4-year term.
Minister for Children Tracey Martin said last year that the inquiry into abuse in state care would take a "broad view of abuse and consider physical, sexual and emotional abuse and neglect".
The Prime Minister said at the time Sir Anand had the "mana, skills and experience necessary" to lead the inquiry.
He has had a long career as a lawyer, judge and ombudsman.