A union says an overtime ban by 240 workers could have an impact on several major export industries.
The workers at Orora Kiwi Packaging in Auckland, Hastings and Christchurch are putting a two-week overtime ban in place at the end of the month.
The company makes packaging for the kiwifruit, meat and wine industries.
Orora is trying to reduce leave and service entitlements after changes to the Employment Relations Act came into effect this month.
An EPMU (Engineering, Printing and Manufacturing Union) spokesman, Joe Gallagher, said the company played a vital role in the supply chain of major exporters.
"There will be a potential shortage of supply: a lot of the supplies are made to order in real time, so potentially if they haven't got the ability to work excess hours, some of these companies may not get their product in time."
Clayton Ford, Orora's spokesman, said they were disappointed by the union's intervention.
"We will work to ensure minimal disruption to our customers, and look forward to continuing talks with our team members to reach an agreement."