The Maritime Union is sceptical about a promise by Fonterra to keep some business with the Port of Taranaki.
Fonterra last month announced it would move less cargo through Taranaki and Timaru and export greater amounts through larger ports like Auckland.
Fonterra says a meeting with the Port of Taranaki on Wednesday did not change its decision to withdraw 65% of its business there.
It acknowledges that will affect thousands of containers, but says it will send enough exports through Taranaki to keep the port viable.
The Maritime Union says it finds that hard to believe.
General secretary Trevor Hanson says the cooperative has not yet shown concern for the impact the changes will have on the region. He says the changes are pointless because they won't result in savings.
Fonterra says the move will benefit the region, because its suppliers and operators in Taranaki will have cost effective and efficient links to the global market.