New figures from the Central Statistics Office show retail sales fell by 0.6 per cent in January amid an ongoing fall-off in sales of new cars.
Consumers are importing more used cars from the UK due to the current weakness in the value of sterling.
The latest monthly numbers indicate retail sales expanded by 1.3 per cent on annual basis in January. However, when volatile motor sales are excluded there was an increase of 1.1 per cent in the volume of retail sales in January and an annual increase of 5.7 per cent.
The sectors with the largest monthly volume decreases were department Stores (-4.2 per cent ) and car sales (-0.9 per cent).
The sectors with the largest month-on-month volume increases were other retail sales (18.4 per cent ) and pharmaceuticals, medical and cosmetic articles (8.1 per cent).
Updated weights
In a statement, the CSO said the latest retail numbers were calculated using updated weights for certain consumer items.
"In 2015, diesel is the main product sold in the fuel retail sector. The proportion of diesel sales is 44 per cent, while it was 37 per cent in 2010 and 22 per cnet in 2005," the CSO's Stephanie Kelleher said.
The proportion of petrol sales has continued to fall, decreasing to 29 per cent in 2015 from 39 per cent in 2010 and 57 per cent in 2005, she said.
She noted that in relation to trade, the sector with the largest weight remained the motor trade, which now represents almost a third of all retail trade, while the sector with the next highest weight is supermarkets, which account for a quarter of all retail trade.
