Cool weather, the return to school and strong demand for flat screen TVs and laptops helped to drive a 21.7 percent rise in weekly sales at John Lewis department stores, the cooperative retailer said on Friday.

Total sales for the group, which also runs Waitrose supermarkets, were up 14 percent in the week ended September 2.

Financial markets scan John Lewis's weekly figures for clues on the health of consumer spending, although its upmarket chains largely reflect the spending habits of middle income shoppers.

Nonetheless, the strong numbers chime with survey evidence suggesting consumers have not been put off by a surprise rise in interest rates in early August.

The Confederation of British Industry reported that retail sales rose at their fastest pace in more than 1-1/2 years in August, while the British Retail Consortium also said sales rise, albeit at a more modest rate.

Last year it was hot and dry. This year it wasn't. That helped to drive footfall, John Lewis said in a statement, explaining the strong rise in weekly sales.

The firm reported record volumes in schoolwear and shoes as parents readied children for the return to school, while demand for electrical goods was also strong.

This mirrored figures reported by the country's biggest electrical goods retailer, DSG International, earlier this week and could allay fears of a drop in demand for goods like flat screen TVs, which experienced a surge in demand during the recent World Cup.