More than 100 jobs will be lost with the closure of Sealed Air's plant in Rotorua.
The plastic packaging manufacturer plans to shut down the site by the middle of next year and expand its Hamilton operation.
The Engineering, Printing and Manufacturing Union (EPMU) said the proposed closure would affect 112 staff, although many were expected to be offered re-employment in Hamilton.
EPMU manufacturing industry organiser Louisa Jones said the union had been working with Sealed Air, which had indicated it would offer generous relocation packages to ease the transition.
"For workers who do lose their jobs there'll be a union-negotiated redundancy package to help soften the blow," she said.