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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Michael Fallon has received reassurances from his US counterpart that security ties with Britain will "endure" following a vote for Brexit.
On Friday, police said it appeared the girl had shot herself in the face with the weapon.
The showers will be slow-moving, heavy and thundery at times, particularly in central and eastern areas.