The Human Right Commission says a bill being considered to deal with a mass arrival of illegal migrants is unnecessary.
The Immigration Amendment Bill would allow for the mandatory detention of such migrants, under a group warrant for up to six months.
Race Relations Commissioner Joris de Bres told a Parliamentary select committee on Thursday that the bill is a setback to New Zealand's long-standing human rights record and international reputation.
He said he was concerned that the legislation and the policy changes it enables are breach New Zealand's obligations under the 1951 Refugee Convention, international human rights instruments to which New Zealand is a party and the New Zealand Bill of Rights Act 1990.
Mr de Bres says New Zealand will not see a mass arrival of boat people, unless there is a massive change in technology and in the cost of ocean transport.