British retailer Marks & Spencer reported a bigger-than-expected drop in non-food sales in the Christmas quarter after deciding to offer fewer discounts just as Debenhams and other rivals were offering more.

In a third-quarter update, rushed out late on Wednesday after trading data was leaked to Sky News, the company said sales of clothing, footwear and homewares slumped 3.8 percent in the 13 weeks to December 29 at UK stores open more than a year.