A union representing immigrants says changes to graduate visas need to be extended to all work visas to end what it describes as inhumane practices.
Starting yesterday, international students can now apply for a three-year open work visa instead of a post-study employer assisted visa, in a bid to cut down exploitation.
The Union Network of Migrants and Indian Workers Association welcomed the change as an end to "bonded labour" for graduates.
But the same problem remained for essential skills work visa holders, they said.
First Union organiser Mandeep Bela said that in a survey of immigrant workers 65 percent claimed to have been exploited.
If workers' visas were not locked into a particular employer and location they would be able to alert authorities of exploitation, he said.
"We urge the government to apply similar regulations on the essential skills visa," he said.
"Here, workers should be able to apply for a visa for their specific skills in a particular industry, such as construction, transport or hospitality, rather than be locked to a specific employer.
"This would ensure their skills are where they are needed the most, and the skills we most desperately need are paid for at a true market rate.
"This would also make it more difficult for these employers to act unlawfully because the employee could just leave and go work somewhere else."
The current situation led to a slave-master relationship and a change was needed to restore the balance of power.
"Other working people would also benefit as migrant workers will not be able to be brought in at a cheaper rate to undercut other workers, migrants will not be able to be used to drive down wages," he said.
It would mean employers had less power to threaten staff into accepting work that breaks employment law, he said.
"In audits done in the past, we've seen some horrifying levels of exploitation," he said.
"Our survey shows this is what migrant workers desperately need. This new legislation needs to go that bit further to ensure we put an end to these inhumane practices."
"Locking-in a migrant worker to one company is essentially enforcing bonded labour," he said.
"Now, at least migrant workers on the [graduate] employer assisted visa will be able to exercise their right to move jobs if they are not treated well or are being exploited, just like any other New Zealander would be able to do. "
Mr Bela said the union was working with one man who was working 60 or 70 hours for 40 hours of pay, paying taxes back to his employer and was threatened with having his visa cancelled if he complained.
He was sacked after calling in sick, Mr Bela said.
Other workers were paying premiums for being employed, so they could ensure their visa would continue.
Immigration New Zealand has been approached for comment.
In a statement, Immigration Minister Iain Lees-Galloway said migrant exploitation took many forms, including workers not getting paid properly, working excessive hours or in unsafe conditions.
"Crucially, far too many migrant workers do not feel empowered to speak up or seek help when they are being subjected to unfair conditions.
"To help develop ways to stop this exploitation, I've directed the Ministry of Business, Innovation and Employment to undertake in-depth research on temporary migrant worker exploitation in New Zealand. This research will guide our future activities to stamp out migrant exploitation, and I note that First Union's Dennis Maga is closely involved in the work.
"First Union's position can be considered as part of this research."
He said he was currently considering advice from MBIE on the parent category, and decisions would be made "in due course".
Yesterday's changes were the implementation of an announcement made in August.
Graduates with degree level 7 or above qualifications are now eligible for a three-year post-study open work visa.
Students with level 4 to 6 and non-degree level 7 qualifications will be able to apply for a one-year open work visa, with an additional year for graduate diploma graduates working towards registration with a professional or trade body.
Students studying level 4 to 6 and non-degree level 7 qualifications outside Auckland will receive a two-year post-study open work visa. After December 2021, that will be reduced to one year.