Red faced bosses at Marks & Spencer have admitted to an embarrassing gaffe which led to millions of pairs of knickers being over-produced. More than 20 million pairs of knickers are sold each year by the company, which is Britain's biggest seller of ladies' underwear. It would normally have six weeks' supplies in stock at any one time, but a mix-up left Marks & Spencer literally sitting on 20 weeks' supplies - more than five million extra pairs of briefs.