"It's very organised ... There's a lot of them that would drive up from Napier, Hastings or the eastern Bay of Plenty to Auckland once a fortnight to the school, just to mark attendance, sign off on work that they haven't even done and it just keeps them going."
Mr Heng said many contractors squeezed up to 20 workers into an ordinary house, breaching safety and fire regulations and undercutting legal backpacker hostels.
One Mt Maunganui house, closed down last month by Tauranga City Council, advertised itself on the internet and Facebook as the South Pacific Hostel.
He said the kiwifruit industry in the Bay of Plenty was one of the worst places in the country for illegal labour.
"Everybody knows about Te Puke. That's somewhere you can go to if you haven't got a work permit or you're not in the country legally. It's pretty famous - for the wrong reasons unfortunately."
Western Bay District Council mayor Ross Paterson said if contractors were using illegal labour, he didn't believe it was a problem.
"I think it is still part of economic growth and getting things to happen. It's allowing us to get on with servicing those orchards and the work that they do and getting the work done."
Asked if that meant illegally low wages were necessary to keep the industry going - a claim made by the AUT report - he said the industry did not need to go down the track of discounted labour.
"I don't think there's savings coming into the industry, I think if there's anybody taking money out of this alleged scheme of cheap labour, it's the contractors."
Kiwifruit Growers Association president Neil Trebilco, of Tauranga, said he was unaware of illegal labour being used in the Bay of Plenty.
"If growers knew about it, then growers must certainly say something but because growers often don't employ directly ..."
The AUT survey found students in the orchards worked for $8 to $11 an hour for up to 55 hours a week, breaching the minimum wage and their student visa, which allowed them to work only 20 hours a week.
Labour Minister Kate Wilkinson has asked the Ministry of Business, Innovation and Employment to investigate.