Workers plan to picket outside Pak'nSave Hastings every weekend until they get a pay rise.
More than 20 First Union members held a demonstration outside the Heretaunga St West store on Saturday afternoon for the second time in two weeks over unresolved pay concerns.
Union organiser Mike McNab said public support for the workers had been growing and they would be "ramping" up their efforts.
Pickets will be held from 11.30am on both Saturday and Sunday this weekend and will continue until the union members get a pay rise, McNab said.
Saturday's picket had been positive with good public support and several customers saying they would stop shopping at Pak'nSave Hastings, he said.