Debenhams has posted a strong Christmas performance as like-for-likes increased by 6.5%, including VAT, in the 5 weeks to December 31.

The department store said sales in December were up 15% year-on-year. The retailer said it had its strongest Christmas week performance ever, with cosmetics up 21% over the week.

In the 18 weeks to January 7, like-for-likes at the department store chain increased 1.4%, although were flat excluding VAT. Online sales rocketed by 34.8%.

Debenhams said it is “pleased” with its performance, taking into account the warmer weather across October and November - which impacted sales of seasonal product lines - as well as low consumer confidence.

The retailer said it had focused on maximising cash gross margin by using promotional events and tweaking product mix. Gross margin guidance for the financial year remains flat.

Debenhams chief executive Michael Sharp said: “Looking forward, we are cautious about the strength of the economy and its impact on consumer behaviour over the remainder of the financial year. 

“We will continue to manage the business tightly with an ongoing emphasis on cost and margin management.  We are confident that the design, quality and value offered by our spring/summer 2012 product ranges will find favour with customers and expect to see some benefit from lower input prices in the second half of the year.”

Within the 18 week period Debenhams opened one new store in Newbury and two international franchise stores in the Philippines. This takes the UK, Ireland and Denmark total to 170 stores, as well as 66 stores in 25 countries.