Stories of migrant workers being exploited, with some paid as little as $8 an hour, have been revealed in a new report.

Photo: 123rf

The report detailed cases of employers taking advantage of new migrants, with limited employment options and limited understanding of employment rights, by overworking them.

In some cases, employers demanded they work for free, the report by Catholic advocacy and aid agency Caritas Aotearoa said.

"These circumstances are depicted as 'normal' by the employer, and then taken on as a 'necessary sacrifice' by some migrant workers," it said.

Caritas spoke to 14 people, including migrant workers, unions and lawyers, between April and June this year.

It noted that the stress associated with having to speak in English with authorities, navigate the legal system, and engage in confrontations, presented barriers for migrant workers to pursue a case, even after they had left a bad employer.

Report author Cathy Bi said the government needed to be more proactive in monitoring employers and could not rely on migrants' reporting incidents themselves.

"There is a gap for vulnerable migrant workers to cross in order to access justice. We can't necessarily expect migrant workers to do this alone, to report cases. And for this to be the only mechanism of accountability over employers," she said.

The story that struck Ms Bi the most was of a girl who worked a shift at a restaurant, but was not paid because her employer told her it was only a trial.

The girl stood up to her employer and won, Ms Bi said.

"What she communicated to me, is that this isn't common for her friends to stand up to the employer, but it is common for employers to say 'Oh we don't pay for this period' or 'We don't give contracts'," Ms Bi said.

The length of time taken by government authorities to investigate reported cases of workplace exploitation was a particular concern, raised by several participants, she said.

Photo: RNZ

Green Party MP Denise Roche said the problem was getting worse as more people moved to New Zealand for work.

"When we don't have enough oversight from our government agencies, and when we don't have the back up of our trade unions because they have been hamstrung by changes in the law, that this government has forced through - it means we set migrants up to be exploited by unscrupulous employers," she said.

There was a reason New Zealand workers often turned down jobs that migrants picked up, Ms Roche said.

"And I get really concerned about allegations from the Prime Minister, for example, that we need more migrants because New Zealanders won't take these jobs.

She said what she had seen was in fact migrant workers being exploited - and New Zealand workers refusing to put up with that.

The Labour Inspectorate said it took migrant exploitation seriously and recognised migrant workers were vulnerable.

It said if anyone was concerned about their employment situation, or the employment situation of someone they knew, they should call the ministry's contact centre on 0800 20 90 20.