The independent Berwick Garden Centre, 46 km away, has lodged plans for an additional store on a two-hectare site, which it is claimed will create 16 full-time and 20 part-time jobs locally.
Shop windows will be whitewashed and "To Let" signs displayed to express locals' anger at the proposal.
Shopkeeper and Dunbar Trades’ Association chair Robin McEwan said: "We’ve already got 10 empty shops in Dunbar and at least five or six are up for sale. If this [development] goes ahead, this is what will happen –at least two thirds of the shops will be empty."
The application was approved by local planners two weeks ago. but has since been "called in" and referred to East Lothian Council’s planning committee. A large turnout is expected at a meeting of committee in Dunbar next Tuesday, where the application will be ruled upon.
Berwick Garden Centre managing director Nick Crabbie told Horticulture Week he had a strong case to put to the meeting. "Currently, a lack of facilities in Dunbar and East Lothian means a leakage of sales of gardening goods to Dobbies (near Edinburgh). Our Berwick store generates £0.5million from passing trade off the A1, and customers say they always visit the town too."