Figures from information group Experian show that the number of people visiting city centre stores and shopping centres in December was down 2.3% on the same month in 2007.
Its footfall index shows that the final two weeks of the year - the weeks beginning December 22 and December 29 - were the only ones since the start of November to experience more shoppers than the corresponding weeks in 2007.
For 2008 as a whole, the footfall index is down 2.4%, while for the eight weeks in the run-up to Christmas, the number of people visiting shops was 1.1% lower than in the same period in 2007.
In comparison, the index for Northern Ireland showed that footfall was consistently up every week except one since the start of September. Experian's Mark Mullally said this appeared to confirm that northern retailers benefited from an influx of southern shoppers taking advantage of favourable exchange rates and VAT rates.
