The New Zealand Press Association said the inquiry of David Cunliffe followed the Labour Department's recommendation that the dispute between the workers and their employers go to a mediator.

According to the news agency, all eight Thai workers - who entered the country legally - had complained that they were ripped off by recruitment agents and employers, often paid below the minimum wage and threatened with being sent home.

They were promised by recruitment agents in Thailand to get lucrative work in the horticulture industry, but were forced to work 60- to 70-hour, seven-day weeks without proper recompense, were bullied by supervisors and ordered to work in other regions.

Their temporary work permits have been revoked by the Immigration Service after a falling out with their employer, horticultural contractor Havenleigh Global Services, and they face being deported.

A married Thai couple, Surachet Kannika and Orasa Khambut, said they paid 10,000 New Zealand dollars (Bt250,000) each to a Thai recruitment agency for an offer of work in New Zealand, flights and expenses. They borrowed the money having been told they could jointly earn NZ$5,000 a month. However, when they began pruning for Havenleigh, they were taking home about $200 a week each.