Costco UK's parent company Costco Wholesale Corporation has blamed the reduction in oil prices and the strengthening

US dollar for a 9% sales drop in the four weeks in January.

Costco refused to give figures for the UK, but claimed its non-US sales - which also include businesses in Canada, Japan and Mexico - were up 9% in the same period.

"The same store sales decline in our international businesses was on a US dollar basis, which has been impacted by dramatic currency fluctuation," Costco UK MD Steve Pappas told The Grocer.