First Union general secretary Dennis Maga is concerned about "rogue employers" taking advantage of migrant workers in terms of pay, pastoral care and health and safety.
It comes after it has been revealed a complaint of possible corruption against an Immigration New Zealand staff member is currently being investigated.
Although the Government agency refuses to say what part of the organisation is implicated, it's understood the complaint relates to the Recognised Seasonal Employer (RSE) scheme, which the government announced an expansion of only last week.
Mr Maga told TVNZ1's Breakfast this morning he had some suspicions about what would be looked at in the investigation, adding that in the past few years First Union had received complaints about RSE "exploitation" in the regions - specifically in Hawke's Bay.
It was hard to narrow down complaints though, he said, with workers going back to their home country, as well as some not wanting to complain for fear of jeopardising the opportunity to come back for work.
Mr Maga said the areas of complaints from the community though were around pay, time records, pastoral care, and health and safety concerns.
"These workers are just being paid barely above minimum wage - now there are also complaints saying how come there are many deductions in their pay slip or in the pay record," Mr Maga said.
"Every time they received the money they kept saying 'how come I only actually earned this much money?'"
There isn't much of a safety net for workers wanting to complain though, so Mr Maga said it was something he wanted to explore with the Government.
"The problem is that there are some rogue employers out there who have a tendency to use the RSE scheme to undermine the [labour] market, and to basically profit from this scheme through the exploitation of the Pacific Islander or RSE workers.
"We've also seen some employers who do not provide facilities for their workers, for example there's no safe water for them, the second is that there's no portable loo."
Mr Maga said that the Government last year announced it's increasing the number of RSE, so they should be increasing the number of inspections of their conditions.
"We feel that in the regions, there are many labour inspectors that are needed in order to conduct the random checking."