Retailers may struggle to keep their shelves stocked in the weeks before Christmas as consumer spending becomes difficult to predict and longer delivery times prevent supplies being replenished at short notice.

With sales on the high street weaker than expected in September, retailers are uncertain about how much they should order for Christmas and could be forced to request stock at the last minute. But with the global freight industry in the grip of its worst crisis in more than 20 years, it lacks the capacity to expand cargo volumes rapidly, or to deliver goods quickly.