Adur Chamber of Commerce - which represents enterprises in the West Sussex towns of Shoreham, Southwick and Lancing - has closed its doors after more than 40 years of representing small companies and has accused supermarkets of forcing small stores out of business.
Beryl Ferrers-Guy, secretary of Adur Chamber of Commerce, said: "These days it would be easier to say which of the big superstores we don't have around here. Small shops just can't compete with the superstores' prices and they're fed up with trying to do so. The superstores don't give anyone else a chance. They're ruthless."
An ongoing £10.5m expansion programme at a Tesco in Shoreham, which is to become a Tesco Extra, had proved to be the last straw, she said. "The managing committee said, 'We're losing members left, right and centre - let's call it a day'. So we did."
A Tesco spokesman declined to comment on the closure of the chamber, but said: "We're expanding in Shoreham purely to do better what we're already doing - to give our customers value for money."