The Maritime Union says overseas booking agents who hire foreign fishing crew to work for New Zealand companies are parasites.
This follows an American journalist's claim he has uncovered further allegations of slave conditions aboard some foreign charter fishing vessels operating in New Zealand waters.
The Maritime Union says it has long argued for a law change making New Zealand companies that charter foreign vessels, responsible for what occurs on board these ships.
A senior fellow at a New York university Benjamin Skinner uncovered further allegations of slave-like conditions aboard foreign charter fishing vessels operating in New Zealand waters.
Last year, the crew of Korean vessel Oyang 75 abandoned the ship in Lyttelton amid claims of poor pay, poor work conditions and physical and sexual abuse.
A report by Mr Skinner of Brandeis University's Schuster Institute for Investigative Journalism relates to another vessel, the Melilla 203.
Mr Skinner says he travelled to Indonesia to speak with crew members who fled the ship in Lyttelton because of slave-like conditions aboard.
He says the Melilla 203 was chartered by United Fisheries, one of the largest fishing companies in the country.
Mr Skinner says three people who deserted the ship because they couldn't take the abuse are in hiding in fear for their lives.
The report has been published in Bloomberg Businessweek, the biggest business magazine in the United States.