First Union protesters in Nelson are due to resume a second day of picketing outside Foodstuffs stores over pay rates.
Organisers were arrested twice yesterday for disorderly behaviour, but Sergeant Malcolm York says he's confident today's picket will be a "nice peaceful protest" and police will monitor the situation.
Almost 15 picketers turned out for yesterday's protest, he said.
Organiser Bill Bradford said the union had the right to represent its members and enter the workplace, and will continue to do so.
The union is protesting over claims workers at South Island Foodstuffs Pak 'n Save and New World supermarkets are paid less then workers at other retail chains.