The Rail and Maritime Transport Union is worried about dangers posed by high stacks of containers, following a incident last month when a forklift driver was seriously injured at Lyttelton Port's city depot in Ferrymead.
Union organiser John Kerr says it is global practice to have stacks of seven containers, but that may not always suit New Zealand conditions.
Worksafe New Zealand has banned Lyttelton Port company from stacking containers seven high.
