A council committee has recommended Easter Sunday trading be opened up in Dunedin.
A hearing last week in front of four councillors focused on the impact of the shops being shut when tens of thousands of Ed Sheeran concertgoers arrive in the city in April.
Retailers are warning of chaos, but unions are arguing shared family and rest time for retail workers is more important.
The council panel has narrowly agreed to recommend that any type of shop be able to open next Easter Sunday, but that the policy be reviewed immediately afterwards.
Paul Watson of First Union said it is a knee-jerk reaction.
"Why is Dunedin going there just because there happens to be one rock concert in town that weekend? They need to focus on the big picture, focus on what it means for worker shaving time off on a Sunday with their family and friends."
Mr Watson said the union will lobby councillors and run a public campaign to reject Easter trading right up to the final decision on 11 December.