A former guard at Manus Island says refugees there are violent and New Zealand should take back its offer to accept them, but Immigration NZ is confident in its vetting systems.
The government has said its offer to re-home 150 detainees still stands, despite revelations of child sex abuse and drug dealing by some.
John Horler, who was a guard in the Papua New Guinea detention centre from 2013 until last month, told Checkpoint he witnessed many episodes of violence.
"At one stage we were allowed to restrain them, we could keep the violence to a minimum. As soon as the centre itself was deemed illegal by the PNG government, we weren't allowed to lay our hands on anything.
"All we could do was watch and report."
Mr Horler said most of the violence was against other detainees but some staff were also injured.
However, Immigration New Zealand has said it is confident its systems for vetting refugees are robust enough to keep out criminals.