LONDON, United Kingdom - John Lewis, Britain's biggest department stores group, reported a rare dip in weekly sales on Friday, 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 percent year-on-year to 72.2 million pounds (118.75 million US dollar) in the week to Sept. 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 percent on the year. Homeware sales rose 0.6 percent, while the electricals and home technology category was up 3.6 percent.

With stores now full of autumn/winter stock John Lewis and rivals, such as Marks & Spencer, Next and Debenhams, will be hoping Britain's warm spell of weather ends soon.

"For the present, there has been very limited promotional activity on the high street but the longer the mild weather continues the more likely retailers will be forced to discount their autumn/winter ranges," said Cantor Fitzgerald retail analyst Freddie George.

John Lewis' sales for the nine weeks to Sept. 13 - the first nine weeks of its second half - were up 9.0 percent, 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 Sept. 13 sales rose 5.7 percent to 118.8 million pounds.