Traders claim proposals to extend a pedestrian scheme will make their life more difficult.
George Street in Hove is closed to traffic daily, except Sundays, between 10am and 4pm.
Brighton and Hove City Council wants to extend the hours until 6pm each evening.
But Keith Bryden, chairman of Hove Business Association, said: "I see the closure as another disadvantage to small shops in an increasingly hostile environment."
He said it would be hard for shops with dozens of suppliers to trade when there was no proper access for deliveries.
Mr Bryden added: "We must attract vibrant businesses to George Street. It must remain a predominantly retail area. We should take care to nurture and hold on to the good, viable businesses we have."
A city council report said: "Experience has shown few delivery vehicles use the street after 4pm so it is not felt an extension would affect deliveries greatly."
Traders will be able to object to a traffic regulation order, which will have to be approved by councillors.
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