Retail organisations are split on Belfast relaxing Sunday trading hours.
A city council consultation ends this week on whether to designate Belfast a holiday resort, which would allow all-day opening on 18 days a year.
Belfast Chamber of Commerce supports the move, believing it would boost retail spending and create jobs.
However, Retail NI, which represents small traders, fears it could be exploited by supermarkets and has "serious concerns."
The move is also opposed by the shop workers' union, Usdaw
It has requested a meeting with the council on 19 May, when a council committee is due to deliberate the move.
The proposal could see large shops in Belfast having their trading hours extended on up to 18 Sundays between 1 March and 30 September each year.
The step is made possible by designating the city as a holiday resort under legislation from 1997.
Last year, a council paper stated there was "a strong lobby" to review Sunday trading, currently permitted from 13:00-18:00.
It said the move would boost the economy, benefit tourism and support the regeneration of the city centre.
Usdaw general secretary John Hannett said the current trading arrangements were a "fair compromise".
"Many shop workers, particularly parents, tell us how important Sunday is to them and their family," he said.
"Often it is the one day of the week when everyone can sit down together for a meal, with many saying they needed the time on Sunday to help their children prepare for the school week."