The Maritime Union says it will fight a decision by Ports of Auckland to sack 28 workers.
The company on Monday confirmed the job cuts from a total staff of about 500 as part of major restructuring and reorganisation of its container terminals.
Ports of Auckland managing director Jens Marsden says there will be a six- week consultation period with staff and unions to discuss redundancies.
Maritime Union waterfront branch president Denis Carlisle says the situation will be discussed at a meeting of its executive in Wellington on Wednesday.
Mr Carlisle says the union is looking at the full range of responses to management actions, including legal action.
He says there will be work available at Fergusson Terminal for some of those workers made redundant.