The axe could fall on workers' jobs at The Warehouse retail stores.
Shopping at the Warehouse
Source: 1 NEWS
The company said it had put a proposal to staff.
The First Union said 180 jobs were on the line at 99 stores.
The Red Shed has been in restructuring mode as it looks to lower costs and improve its competitiveness.
It has already made changes to its marketing and human resources teams and moved its in-store strategy to an everyday low-price model.
The company said it was seeking feedback from staff before deciding on any changes.
First Union organiser Kate Davis said it was disappointing.
"Members don't know if it'll be them who get the cut, it is largely supervisors who are affected. What we do know is that supervisors tend to be the older career retail workers who have solid hours," she said.
Ms Davis said workers had until next weekend to give feedback on the proposal.
"Will this kind of restructure help their image problem? Or will it add to their image problem?... We are calling on the community to let The Warehouse know and then we'll work with the members to find out how they wish to respond," she said.
The Warehouse said it was making no further comment while it consulted with staff.
Meanwhile, workers at Pak'nSave in Hastings are picketing over pay and conditions.
First Union said more than 50 workers - including butchers and bakers - would be handing out flyers and speaking with the public this afternoon.
The workers are accusing the company of treating them like secondary citizens.
But Foodstuffs - which owns Pak'nSave - said it was disappointing the picket was going ahead when both sides had agreed to mediation.
Foodstuffs said it believed it was meeting its employment terms.