John Lewis has reported a slump of 8.3 per cent in weekly sales, which it blames on a combination of sunny weather and coverage of the global economic situation.

For the week to September 27, sales only grew on the Monday and the worst day of the week was Saturday, when the sun was out.

John Lewis director of selling operations Dan Knowles said it had been a “very tough trading week”. He added: “Sales declined by 8.3 per cent in what we know is a very difficult market – a market in which we continue to grow our share.”

Of the retailer’s three new branches, Leicester was helped by strong trade in catering, beauty and furnishing advice. It said Liverpool also prospered, while in Cambridge electricals and fitted kitchens led the way.

Some of the worst-performing stores included Bristol’s Cribbs Causeway, down 24.6 per cent; Southampton, down 24.5 per cent; Peterborough, down 22.7 per cent; and Milton Keynes, down 20.3 per cent.

The Christmas shop opens fully this week and Knowles said: “The market is tougher than it’s been for a long while – and John Lewis will be rigorous in keeping doing the right things for partners and customers, driving sales, taking share,and managing our cost base for long-term development.”

Waitrose said trade remains challenging, with sales down by 0.7 per cent. However, it maintained strong promotions drove growth in many areas including fruit, biscuits, sausages and spirits.