The UN Committee Against Torture is calling on the Government to do more to uphold and protect the human rights of all people.
In a new report, the committee has welcomed some new measures taken in this country, such as the introduction of police safety orders and the Vulnerable Children Act.
But it has expressed concern at the over-representation of Maori in prisons, and the use of solitary confinement for mental health patients.
It is also concerned about the lack of funding and autonomy for the Independent Police Conduct Authority (IPCA), violence against women and children, high rates of violence in the privately-run Mt Eden prison, and the failure to incorporate human rights into legislation.
A human-rights lawyer, Michael Bott, said the committee's latest findings showed vulnerable people were not being adequately protected in New Zealand.
Mr Bott said the report's authors were clear the Government should be doing more to uphold human rights.
"Whereas at the moment, what appears to be the case, is that we appear to be - shall we say - reducing and trying to particularise and minimise our obligations," he said.
"In other words, we pay lip service. So overall, if this was a report card, it would be a fail. Or, probably, at best, merely an 'achieved'."
He said human rights were essential for protecting individual freedoms and the Government needed to enshrine human rights in legislation.
"When you mention human rights, there's a groan and there's this idea that there are people just being woolly, sort of, bleeding-heart do-gooders and that's not the case," he said.
"The reason we have these obligations is to protect us all. It's about basically about having checks and balances on the excessive use of state power."
As well as torture, the committee also monitors cruel, inhuman or degrading treatment or punishment.