Gill Bonnett, Immigration Reporter
An MP fighting for anti-trafficking legislation says it is hard for prosecutors to take cases to court - but he is hopeful his bill will turn the tide.
RNZ has revealed that children are among those enslaved, sometimes after being adopted overseas and without their new parents being vetted.
National MP Greg Fleming hopes to get the law passed, with possible cross-party support for a wider bill.
He is waiting to hear whether parliament's business committee will allow the scope of his first members' bill on slavery offences and penalties to be expanded.
He also has a second members' bill in the ballot - to introduce a requirement for companies with turnovers of more than $100m to carry out due diligence reports into slavery and other workforce complaints in their supply chain and operations.
With cross-party support, that could become the first bill to make it to parliament without being picked from the the members' ballot - the biscuit tin - under a new parliamentary avenue.
Fleming said while neither bill included a modern slavery commissioner, he predicted that will happen in a few years.
"Part of the challenge we have been having in New Zealand for many years now is the inability to effectively and efficiently prosecute known cases of human trafficking," he said.
"I think most people have no idea of just how commonly occurring trafficking is in a place like New Zealand and I think that is part of the reason why we haven't seen movement in the legislation space.
"My role is to push for the legislative change that so many people in the NGO space have been pushing for years because - very sadly, lamentably - there are a number of cases like this happening every year in New Zealand."

A third bill?
Draft legislation that would encompass the issues in Fleming's bills - as well as introducing a modern slavery commissioner, and more services for victims - was drawn up last year by a group of trafficking specialists. There was hope at the time that it could garner the 61 non-executive MPs needed to allow it to be directly introduced to the House, skipping the members' ballot.
Labour MP Camilla Belich, who has backed the bill, said that has not yet eventuated.
"From Labour's side we are very supportive of the comprehensive bill that was drafted by the experts. It's very much in line with the decisions that we announced prior to the last election in relation to modern slavery and would really bring New Zealand into line with other countries that do have legislation for modern slavery.
"So we have put that offer out there and remain open to joining forces with the National Party or other political parties in parliament to see if we can get that comprehensive bill introduced. That offer remains on the table. My understanding is that there there isn't the appetite to support this particular bill at the moment, which is very disappointing not only for us but for many of the organisations who've worked really long and hard to try and get this legislation in the statute books in New Zealand.
"But also we have to think about the people who are affected by this type of human trafficking and essentially modern slavery that happens in our supply chain and the fact that practice can continue without an adequate statutory response in New Zealand is very, very serious - and something that I'm sure, weighs heavily on the minds of of many."