Unions are deeply concerned the government is pushing ahead with plans to prevent private contractors from challenging their employment status through the courts.
Consultation on the move is taking place this week, ahead of rideshare company Uber's attempt to overturn a major court case that earlier found in drivers' favour in the Employment Court.
Council of Trade Unions president Richard Wagstaff said the issue was shaping up to be one of the biggest battlegrounds in employment law over the coming years.
"We would see this as the most egregious attack on worker rights in decades."
ACT campaigned on amending the Employment Relations Act, so those who signed up to be independent contractors could not then challenge that status in court.
Minister for Workplace Relations and Safety Brooke van Velden is in charge of the policy but declined multiple requests for comment.
The coalition agreement between National and ACT states they would, "maintain the status quo that contractors who have explicitly signed up for a contracting arrangement can't challenge their employment status in the Employment Court".
Despite that position, the Ministry of Business Innovation and Employment's consultation invitation referred to it as a "potential change".
Business NZ director of advocacy Catherine Beard said contracting had always been part of a flexible workforce, that "suits a lot of people, suits a lot of workers and their lifestyles".
"It's a really valid business model so we just want the government to confirm the status quo."
Parliament should be making the laws - not the courts, she said.
Beard wanted more clarity around "what constitutes a contractor so that there's no kind of misunderstanding and we don't have companies ending up in court like Uber has".
MBIE's call for feedback indicated the government wanted to put more weight on the intention of the parties involved.
But Wagstaff said this ignored the power imbalance that exists between workers and employers.
"And having an opportunity for employers to wrongfully categorise workers without any rights, knowing there can be no legal comeback at all, is really serving up to the unscrupulous exactly what they want."
The move came as four Uber drivers continued their fight to be recognised not as contractors, but employees - with holiday pay, sick leave and other entitlements.
The Employment Court ruled the four drivers were employees but Uber took the decision to the Court of Appeal, which was yet to make a ruling.
First Union spokeswoman Anita Rosentreter had advocated on behalf of the drivers and said their right to fight was a critical one.
"Being an employee is the gateway to having any work rights in this country, and it's really, really important that that as a concept is upheld."
The problem was not with contracting work, but when workers who should be employees had been mis-classified, Rosentreter said.
"Often what you're going to find is they're actually earning less than the minimum wage, and they're getting none of the rights that come with being an employee around that, and that's a really, really precarious position for a worker to be in, and it leads to exploitation."
Wagstaff agreed, pointing out cleaners who had challenged their status and won greater working rights.
"These are the people who have been miscategorised as contractors and have been missing their fundamental rights, and the courts have rightfully recategorised these people as employees.
"This won't just be about Uber, although that is greatly concerning."
OIA documents showed van Velden was planning to meet with Uber.
Rosentreter confirmed to RNZ the minister had not yet approached First Union to set a meeting with the drivers.
"I would hope that if the minister was meeting with Uber that they would also extend an invitation to us as well, to speak to the union that is representing Uber's drivers to get that very crucial other perspective."
Labour workplace relations spokesperson Camilla Belich called the change a "worrying" prospect.
"I think it's worrying that we have a party in power now which is proposing to take away the right of employees to test their employment status in court."
Belich the meeting between Uber and van Velden could mean the minister was looking to change the law as other countries had done, "to allow a third status of employment that isn't an employee or isn't a contractor".
