Under the Prostitution Reform Act, it is illegal for any migrant on temporary visas to engage in sex work even though it is legal for New Zealand citizens and residents.
"All of the migrant sex workers...even the most vulnerable, came to New Zealand and engaged in sex work of their own choice rather than being trafficked," said Associate Professor Gillian Abel, co-author of the report.
A majority of those interviewed said they chose sex work in brothels over lower paying minimum wage work to fund their study or travel.
The biggest stress for the sex workers was being reported to authorities and deportation, the report said.
"They were not worried about their safety as a sex worker but knew their work was illegal and worried if they came to the attention of authorities, they would be deported and this 'black mark' would make travel to other countries difficult," said Abel.
In the past three years, deportation liability notices have been served to 38 migrant sex workers and 27 have been deported.
"This allowed unscrupulous people aware of their immigration situation to blackmail them and avoid being reported to the police," Abel said.
Non-English speaking sex workers were the least likely to know about and access health and welfare services, and also the most likely to be subject to exploitation and sexual violence.
These included being forced to work long shifts, pay fines and being forced to offer unprotected sex.
Abel said consideration should be given to repealing Section 19 of the Act because it created conditions in which exploitation could flourish.
"Exploitation could be addressed if migrant workers were more able to report disreputable brothel operators and others to authorities without fear of deportation," she said.
Participants in the study included sex workers from Singapore, United States, China, Britain, India, Germany, Brazil and Vietnam.
Peter Devoy, INZ's assistant general manager compliance, said the research was a good start but "only the first step" towards developing an understanding of migrant sex workers in New Zealand.
"More work needs to be done to understand the most hidden and most vulnerable migrant sex workers...including the scope and scale of the population," Devoy said.
Devoy said anyone being forced to work in the sex industry illegally can contact MBIE on 0800 209020, email info@employment.govt.nz or contact Crimestoppers anonymously through the Ministry's website.
Dr Michael Roguski of Kaitiaki Research and Evaluation worked alongside Abel on the study.
