Policies tying migrants to single employers need to be dropped, a migrants advocate says, after police laid charges in a probe into exploitation.
Police have charged a man with three counts of rape and say their investigation into a suspected human trafficking ring is likely to spread to other districts.
Migrant Workers Association spokesperson Anu Kaloti said she was "shocked and disgusted" by the news and is calling for the new immigration minister to do more to protect migrants.
It was "a new low" for the country, she said.
A 44-year-old man has been charged with three counts of rape after a distraught woman approached police for help two weeks ago.
Police and Immigration immediately launched a joint operation, called Operation Wentworth.
Detective Senior Sergeant Sally Patrick told RNZ the man will also likely be charged with trafficking although police first have to seek the solicitor-general's consent to lay those charges.
She said there was a strong possibility of other victims, in Hawke's Bay and elsewhere, and she has urged people to come forward.
Kaloti said she was "extremely worried" about migrant exploitation in New Zealand. Migrants were the most vulnerable workers in any workforce and did not have the protections they needed despite organisations like her as well as trade unions calling for more action for a long time.
"It's unfortunate it's come to this and victims have had to go through things like rape and had to human traffic for some action to be taken."
Kaloti said the new Immigration Minister Erica Stanford needed to step up and make some policy changes to avoid similar "horrendous" incidents.
She believed these arose from both long-running systemic problems as well as an influx of migrants during the Covid-19 pandemic once the borders re-opened.
She said her top reform would be ending the tying of migrants to a single employer.
"That's where most of the exploitation has been happening."
There had been a "horrendous" number of scams linked to the accredited employer work visas which was meant to be "the silver bullet" for the immigration sector.
Over the years governments had failed to act on many of the findings of reviews and research, Kaloti said.
"It's time to take some action."
She wanted the accredited employer work visa scheme halted until it was reviewed by Immigration.
"Too many rogue employers have got through that scheme."
Another problems was that the number of people gaining residency visas has been falling while those on temporary visas for a longer period have been increasing.
Also immigration settings for a pathway to residency needed to be reviewed. There was too much emphasis on higher skilled migrants.
"Every person in the workforce brings skills and their skills are to be respected and to be rewarded with equity so our pathways to residency still need a lot of work," Kaloti said.
Anyone with information can contact police on 111 and quote file number 231129/1010 or call Crimestoppers on 0800 555 111, police said.
Immigration New Zealand declined to comment further, as the investigation is ongoing.