A human rights lawyer says the exploitation of migrant workers in New Zealand may be widespread.

In a case described as modern day slavery of five Filipino workers, an Auckland restaurant owner has been jailed for two years, and her husband sentenced to eight months home detention.

Lawyer Craig Tuck says reporting this sort of behaviour is difficult for those affected, because they are vulnerable.

"In New Zealand because there is the threat of police intervention and deportation, many people don't report it.

"We do know it's present in the maritime sector, the agricultural and horticultural sectors."