When Helen Clark's Labour government brought in a law that would create waves of undocumented children, even the immigration experts had no idea of the impact it would have on thousands of lives.
The 2006 Citizenship Amendment Act ended automatic citizenship for children born here to overstayers or parents with temporary visas. It was also supported by the National party.
"It is only recent because these children are now finishing high school and realising that their life has now come to an end, they don't have any options as to what to do."
At the time Helen Clark said she was concerned about incidents of people flying to New Zealand for a short time and having babies here to ensure they gained passports, known as "birth tourism".
"Every year now more and more children are going to be coming out of high school and realising that they can't study, they can't go and get jobs because it would be a breach of the law for employers to employ someone who's here unlawfully. So they can't work, they can't study, they can't travel, they just simply cannot do anything."
McClymont says he has not had a satisfactory response from the government to his suggestion that New Zealand follow Australia and Britain by giving children birthright citizenship after 10 years of habitual residence.
"Really, it's hard to see what the justification is for punishing these children. Nobody is making the argument that these children have done something wrong and that they deserve to be punished.
"The only potential argument is that these children are being punished as a deterrent for others against having children here in New Zealand," he says.
"It's just unfathomable as a society that we can actually do this to children and use them for this purpose. There doesn't seem to be any moral justification whatsoever for treating them so badly."