John Lewis, Britain's biggest department stores group, reported a rare dip in weekly sales today, becoming the first major UK retailer to say shoppers were delaying purchases of winter clothing because of unseasonably warm weather. 

The employee-owned firm said department store sales fell 3.5% year-on-year to £72.2m in the week to September 13. 

"With children now back at school, thoughts would usually turn to winter essentials; however, the unseasonably warmer days are delaying these purchases," John Lewis said. 

"Footfall was restricted on the year due to less promotional activity on the high street," it added. 

The retailer's fashion sales fell 13.1% on the year. Homeware sales rose 0.6%, while the electricals and home technology category was up 3.6%. 

John Lewis' sales for the seven weeks to September 13 - the first seven weeks of its second half - were up 9%, a big outperformance of the wider sector. 

The firm, whose business model has been lauded by Prime Minister David Cameron, has been winning market share from rivals in recent years due to its strong online offering, modern stores and a relatively affluent customer base. 

The John Lewis Partnership also owns upmarket grocery chain Waitrose. Its week to September 13 sales rose 5.7% to £118.8m.