Newshub has spoken to two Filipino builders who say they had to work on a construction site with no safety gear - two of many foreign workers who have been exploited in New Zealand.

An Auckland University study has uncovered severe exploitation of foreign workers in New Zealand.

Workers interviewed for the study reported earning only $4 an hour or even no pay at all. In some cases shifts were 18 hours long and up to 90 hours a week.

Some workers had no contracts, no holiday pay and no bathroom breaks.

And many of them told researchers they were frequently insulted, and verbally or physically abused.

Newshub met two Filipino builders who were brought to New Zealand by a labour hire firm who promised them work from day one.

On arrival in the country, they say there wasn't even a job to go to, nor proper accommodation.

"Eight days, no work," one builder told Newshub.

And during that time they slept on the floor, "only on the foam [mattress]," he went on to say.

When they did start work, they were told to get on with the job - four storeys up with no safety gear.

First Union National Organiser Dennis Maga says the conditions are far from safe.

"There's no health and safety training for these workers. They're actually endangering their lives - working there without any harness on a four floor building. So that is really problematic."

Even after risking their lives in the workplace. The men say they have now been unfairly dismissed. Sacked over claims of substandard work, which they say are untrue.

Their experience forms part of a new study by researcher Dr Christina Stringer, who concluded exploitation is widespread.

"There's some appalling treatment of the workers."

Dr Stringer interviewed 105 workers as part of her research and said conditions could be likened to modern-day slavery.

"Some became quite emotional ... they shed tears. A lot of them expressed fear, frustration, anger."

The study identified foreign education providers as a major part of the problem and quotes previous Newshub investigations.

As part of our series on the International Academy of New Zealand (IANZ), we can now reveal a former worker at the school says staff, most of whom were on temporary work visas, were told by bosses at the school to alter official documents.

One woman says some students at IANZ ended up working there illegally, many desperate to gain permanent residency.

"They call it 'help'...for the students that are working for them."

Newshub asked how many students she thought worked without contracts at IANZ.

"More than five," she answered.

The study highlighted frustration among some migrants at a lack of action from authorities.

Our source laid a complaint with Immigration NZ five months ago but has heard nothing since.

She says she is feeling "frustrated… dismayed" at the lack of action.

Immigration NZ didn't want to comment - except to say that "IANZ issues are still being worked through by several agencies".

If you have further information regarding worker exploitation, email Michael Morrah:michaelmorrah@mediaworks.co.nz

Newshub.