Rubbish pay is behind Kiwis' reluctance to work certain jobs, not their drug habits, says First Union leader Robert Reid.
Immigration is at a record high, and the Prime Minister on Monday said migrants are needed to fill vacant jobs because some Kiwis are lazy and would rather do drugs.
"Go and ask the employers, and they will say some of these people won't pass a drug test, some of these people won't turn up for work, some of these people will claim they have health issues later on," John Key told RNZ.
"They're also living in the wrong place, or they just can't muster what is required to actually work."
The comments made international headlines, gracing the pages of the Telegraph and the Guardian.
Mr Reid says First Union members were offended by Mr Key's comments, and that Kiwis would happily fill the roles if the pay wasn't so bad - often illegally so.
"When we investigate what they're getting paid, it's usually if not the minimum wage, even less than the minimum wage."
He says lax immigration rules are being used by the Government as "a form of labour trafficking" to keep wages down, and that many migrant workers don't get the travel and holiday pay they're entitled to because they're afraid of losing their jobs or being deported if they speak out.
"You don't just open the floodgates so that anyone can come. There needs to be an assessment of what industries need extra labour, what skills are needed, what New Zealanders can be trained for," he says.
"For people to take jobs at the very low end of our pay scales is just another attempt at trying to pull down wages and conditions in New Zealand."
Earlier this year, Deputy Prime Minister Bill English called Kiwi workers "pretty damned hopeless", and said "dozens" of employers agreed with him.
"They won't show up, you can't rely on them and that is one of the reasons why immigration is a bit permissive to fill that gap".