Unite Union worry a new approach to punishing employers who exploit migrant workers will not be enough to beat the "systemic" problem.
From the beginning of April there will be a blacklist of employers who have been penalised for exploitation before, and so will face a temporary ban.
"They will be the subject of a stand down period of between six months and two years, where they simply cannot accept applications for labour market tested work visas," said Immigration Minister, Michael Woodhouse.
Unite Union's National Director Mike Treen said the "problems are not rogue employers, they are systemic because workers are in vulnerable positions".
The Human Rights Commissioner Jackie Blue said migrant exploitation is one of the biggest issues facing businesses.
"A strong message needs to go through, we do not tolerate migrant exploitation, our reputation and our economy is going to depend on the use of migrant workforce."
Opposition parties said the blacklist does not go far enough and the real problem is not enough labour inspectors to carry out spot checks or support vulnerable workers who are too scared to speak out.
There are currently 58 inspectors nationwide and 200,000 temporary work visas handed out in New Zealand each year.
"They are actually overwhelmed by the complaints they've already had," said Mr Treen.
"We've significantly increased the resources given to both the labour inspectorate and the immigration compliance team by two thirds in the last two years," said Mr Woodhouse.
Construction, dairy, fishing, horticulture, viticulture and hospitality are all industries which an Auckland University study said have exploited migrant workers.
"There are huge problems in those areas," said Ms Blue.