Traders in Southwick town centre are fighting a rent rise of almost 60 per cent.
And Adur Council wants the hike backdated to last June, when it says a rent review should have been completed.
Outraged traders in Southwick Square have the backing of Adur and District Chamber of Commerce.
Chamber secretary Beryl Ferrers-Guy said: "Such a massive increase is outrageous.
"It is based on the fact the council has succeeded in obtaining a similar rent from a charity shop - one that pays no rates, has volunteer workers and stock donated by the public, hence its willingness to pay a higher rent.
"This is hardly grounds on which to base the rents of smaller shopkeepers whose overheads, particularly their rates, are already a burden.
"While an increase is expected, it should be one that can be more easily absorbed.
"I fear the square will lose many of its smaller stores, which will not only be devastating for the owners but will also have a serious impact on those local residents who are unable to get to the superstore complexes."
Traders in the square have to compete with six superstores within a five-minute drive.
When the superstores at nearby Holmbush were built, rents were frozen in Southwick Square for five years because of the expected impact.
Since then two shops in the square have been on the market and another two have been turned into charity shops.
Martin King, a former Liberal Democrat councillor, said: "If the council goes ahead with these increases it may make a short-term profit for the first 18 months to two years, but in the long term it will be losing an enormous asset."
But Tory leader Neil Parkin said it was council officers' responsibility to get a good deal for taxpayers.
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