Former patients of Lake Alice Hospital have been told police inquiries have finished and there will be no prosecutions.
Police investigating allegations by 40 people announced on Tuesday that no criminal charges will be laid against Dr Selwyn Leeks.
He was accused of abusing patients at the central North Island psychiatric institution's Child and Adolescent Unit between 1972 and 1977.
The ex-patients now intend to take their case to the United Nations.
A survivor and founder of the group Survivors of Lake Alice, Paul Zentveld, told Nine to Noon he had known what the decision would be since November last year.
"We needed this case to be closed. The UN can't act, no one can do anything until the police have exhausted all avenues of inquiry.
"So (it's) a very good day for all concerned and now we can move forward."
The executive director of lobby group the Commission on Human Rights, Steve Green, says the investigation was not thorough. He says the complainants were not interviewed by police.
The police say as part of the investigation all complainants gave them written statements.
