Independent retailers saw sales fall back 3.8% in the quarter ended September.
The BSSA said that the figures showed trading for the year to date was down 1.6% against 2007.
BSSA chief executive John Dean said the data showed that small and medium sized businesses need urgent help from the Government and called for further interest rate cuts.
Dean said: "The figures further underline the serious trading conditions being faced by small independent retaielrs currently and emphasise the need for the Government to take rapid and imaginative action before many businesses become insolvent. A further significant cut in interest rates is needed in an effort to encourage the consumer to start spending again."
The BSSA Sales Monitor collates retail sales data from non-food independent retailers on a quarterly basis.
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