A union representing about 2000 workers employed at retail giant The Warehouse says conditions are getting worse.
National Distribution Union (NDU) members are attending stop-work meetings around the country, starting on Tuesday in Whangarei.
The NDU says a recent restructuring plan known as Project Invigorate is leading to increased workloads and unfair shift work with no pay increases.
NDU spokesperson Bill Bradford says the restructuring involved a move from full employment to casual work.
He says The Warehouse has been at the forefront of introducing a style of work that Walmart in the United States is best known for.
'It's a style of work that leaves workers feeling very insecure and overworked and underpaid.'
He says negotiations for a new collective contract have stalled and workers are fed up.
The union's campaign manager, Simon Oosterman, says some staff are so frustrated with their working conditions they're prepared to walk off the job.
He says staff are also angry at a clause in a new collective contract that would give the company the right to increase staff hours and work days without them being able to challenge it.
The Warehouse rejects unfairness claims
The Warehouse rejects the union's claim of worsening work conditions, saying the company is fair on staff.
The firm's general manager of operations, Karl Parker, says a Project Invigorate aims to move workers to peak shopping times when they are most needed, but he says roster changes have been made with careful negotiation.
'It hasn't been a forced move in most cases. It's been through high levels of discussion, consultation and also working within individuals' personal circumstances.'
He says the company is keen to negotiate further with the union.