A visiting delegation from the United Nations is critical of a law and order reform going through Parliament.
The Public Safety (Public Protection Orders) Bill will allow the High Court to detain dangerous prisoners indefinitely, even after they have completed their prison sentence.
A delegation from the UN Human Rights Council has been in New Zealand for two weeks examining New Zealand's record on arbitrary detention.
Its leader, Mads Andernas, says the proposed law is not in compliance with the New Zealand Bill of Rights and international law.
Mr Andernas says there must be compelling reasons to keep a prisoner detained on preventive detention after they have served their sentence and there must be regular reviews by an independent body.
But Justice Minister Judith Collins says the bill has strong checks and balances to ensure orders are applied correctly.
A select committee hearing of the bill will be reported back to parliament next week.
