Amnesty International said it was alarming that New Zealand continued to detain asylum seekers in remand prisons.
The organisation has just released its annual report on the state of the world's human rights and says New Zealand still has plenty of room for improvement including in its treatment of those seeking asylum.
Amnesty's executive director in New Zealand Grant Bayldon said about 10 asylum seekers were being held at Mt Eden and Waikeria remand prisons, with one being detained since March 2015.
He said they had not been detained because they had done anything criminal, and the length of stay in the remand prisons varied.
Mr Bayldon said there had been cases where asylum seekers had been assaulted by other prisoners.
Amnesty said the report also highlighted New Zealand's ongoing challenges with family violence, child poverty and Maori being over-represented in prison.
It said a government review of the country's annual refugee quota dragged on, despite urgent calls for it to respond with integrity to the global crisis by increasing the quota, which remained at just 750 per year.
"New Zealand's own announcement to take an emergency intake of 600 Syrian refugees over three years was a welcome and life-saving response but didn't come anywhere close to doing its fair share in the global refugee crisis. The time has passed for token gestures, New Zealand must take its global responsibilities seriously," Mr Bayldon said.