About 700 workers at two Countdown distribution centres in Auckland have walked off the job for three days.
First Union said the Auckland workers were having to deal with spiralling rent and housing costs, and were asking for what they think is a fair pay rise.
Organiser Jared Abbott said the workers had been bargaining for a number of months, and had had enough.
They were looking for a 4.9 per cent increase, in line with the latest annual Consumer Price Index (CPI), in order to settle.