Cases of migrant workers being paid less than the minimum wage are widespread, according to research from the AUT Business School.
Researcher Danae Anderson's findings support a ONE News investigation which found some small business owners in Auckland are profiting from overseas workers by offering work for as little as $8 an hour.
"We're seeing it across a large number of sectors," Anderson told TV ONE's Breakfast.
"In the primary industry, the horticulture sector which I researched, but also what Amy (Kelley, ONE News reporter's) research is saying is the same findings that I've found exist in Auckland's service sector as well."
Anderson surveyed 93 people at five Bay of Plenty kiwifruit orchards, and found they were all being paid illegally. She said almost all of those people were from India, and had been hired by contractors who were making a profit from underpaying their staff.
"A lot of them, particularly the Indian students I've surveyed, have large loans that they've taken out for education. So not only are they living here and having to pay reasonably high costs of living here they're also servicing large loans with high interest rate back in their home country."
Anderson said migrants are sold a vision of New Zealand which fails to live up to expectations when they arrive.
"I think they're sold something which they find isn't the reality," she said.
"But when you look at the illegal side of things there's a lot of pressure. Communities rip off communities to be blatant, you saw the Chinese last night, they were hiring other Chinese. Indian contractors rip off other Indians so it very much stays within the local communities."
When probed about the $13.50 minimum wage by ONE News, some employers denied knowing it existed or said the salaries offered to workers were only trial rates.
Labour's spokesperson for labour and immigration issues, Darien Fenton, said it may be time for a high-level inquiry into the issue given the growing number of examples of migrant worker exploitation.
"The Government must urgently lead an investigation into the businesses exposed by TVNZ's ONE News and earlier examples of worker exploitation," he said.
Anderson said there was no way of knowing how many people were being underpaid by their employers.
"Effectively we are looking at illegal workers, these people are invisible statistically because they're not going to run to the Department of Labour because they are in breach of their visa conditions.
"It is unsustainable for industry in New Zealand. The horticulture industry, if they keep going down this track, cannot keep going using this sort of labour practice."
The Department of Labour is expected to comment on the illegal
wages tonight on ONE News at 6pm.