The Rural Contractors Association has accused the Council of Trade Unions of having a hidden agenda, to seek a minimum 30-hour week for all employees after the election.
The association's comments relate to part of the Recognised Seasonal Employer Scheme, which is designed to overcome labour shortages in the horticulture and viticulture industries.
Under the RSE scheme, workers from the Pacific Islands are guaranteed at least 30 hours of work a week, but New Zealand workers are not given that guarantee.
Rural Contractors Association executive director Roger Parton says this is discriminatory and should have attracted criticism from the CTU.
He says the association has a very strong suspicion the CTU will push for this condition for all contractors after the election if Labour is re-elected.
Mr Parton fears rural contractors may go out of business if the CTU has its way.
But CTU president Helen Kelly says the council is not pushing for a mandatory 30-hour week for New Zealand workers.
She says the industry needs to smarten its act to make the work more attractive for New Zealand workers.