Unions in New Zealand say they oppose any expansion of the Recognised Seasonal Employer scheme.
The RSE allows Pacific workers into New Zealand on short term visas to work in the horticulture sector.
The criticism from New Zealand's Council of Trade Unions comes as talks on the PACER Plus regional trade deal resume in Samoa, with more seasonal work a critical element in getting the island nations onboard.
The CTU's Bill Rosenberg says the RSE scheme is threatening to make Pacific workers a dominant source of employees in the industry.
"There have been suggestions from the PACER PLUS nations that the RSE scheme or something like it be expanded into other industries. We would be very concerned at that because we think that the problems that would arise there would be similar to or even more concerning than what has happened in the RSE scheme."
Bill Rosenberg says New Zealand's RSE scheme could be under more pressure given Australia's plans to expand its seasonal programme.