Stephen Robertson, director general of the British Retail Consortium, said it looked like the modest sales revival seen in September was something of a "false dawn".
The disappointing figures are a reminder of the difficult economic realities many are still facing.
Falling consumer confidence means people are limiting spending to essential items and are cautious about committing to big-ticket and discretionary buying.
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The foreign secretary has criticised internet and social media giants for failing to detect and remove extremist material posted online.