The strawberry farm each year employs about 90 Tongan workers under New Zealand's Recognised Seasonal Employer scheme.
Lynda Ashby was in Nuku'alofa last week and said the majority of the Tongans were hard working but a few are damaging the country's reputation due to their heavy consumption of alcohol.
Radio Tonga quoted her saying the alcohol use had led to brawls.
Ms Ashby said if the problem was not solved the farm might look for another country in the Pacific to supply its workers.
