About half had their visas extended by INZ while an employment case was taken by the union against the hire company involved, National Personnel Limited.
But a settlement has now been made out of court. Treen says four of the workers have now been asked to leave the country, despite having an employer willing to keep them on.
"We don't think that's fair. I think there's a moral responsibility to facilitate every one of that group to be able to stay - at least three years, to give them a chance to recoup the money."
The workers were promised steady construction work, pay of up to $6000 a month, and that they'd eventually be able to bring their family to New Zealand.
Treen says the workers helped INZ with their investigation, and the notice to leave does not live up to promises of fairness made by Immigration Minister Iain Lees-Galloway.
"They're devastated, they're just in tears. They arrived to find the wages and the conditions and situation just wouldn't allow them to earn the type of money they had been promised, in the time of the visas that they had.
"I can't imagine the consequences of this for this group of workers. One has told me coming to New Zealand was the worst experience he's ever had."
Treen says all of the workers Unite represents received a payment, as part of the confidential settlement with National Personnel Limited, but it wasn't close to what they originally paid. He says the firm has also employed them.
"I think this highlights a problem that we don't really have a proper system of support and advocacy - we've got quarter of a million people in New Zealand on temporary visas. There's just repeated examples of terrible exploitation, the system breeds this vulnerability and exploitation.
"We need an agency to actively promote and defend workers' rights - Immigration New Zealand's overwhelming culture is to treat nearly all of them as cheats and scrounges, rather than just workers trying to survive.
"It's wrong that INZ is part of the same Ministry that is also in charge of protecting workers rights, and minimum labour standards - I think the culture affects the whole organisation, so it can't adequately protect these quarter of a million workers."
Their recruiter Peter Li, or Wenshan Li, has also denied personally receiving any of the workers' money. And National Personnel Ltd has said it did not know or approve of the Chinese workers Li brought over.
Immigration NZ and Immigration Minister Iain Lees-Galloway have been approached for comment.
- RNZ
