Zespri accuses Turners & Growers of trying to divide the kiwifruit industry.
The exporter's control over the industry is being challenged by Turners & Growers at the High Court in Auckland.
Turners & Growers says current regulations that give Zespri a monopoly control over most export markets are unlawful.
Instead, it wants a system in place that allows growers to export alongside the company.
Zespri says 90% of growers are happy with the current collaborative marketing regime and a previous Labour Select Committee recommended that no changes be made.
It describes Turners & Growers legal bid as a waste of money.
The hearing is set down until the end of the week.