Marks and Spencer shares fell by almost a a quarter on Wednesday after a profits warning from Britain’s biggest clothing chain prompted analysts to slash profit forecasts for the retailer.

Citi, one of the house brokers, said it expected consenus forecasts for full-year profits to come down by 20 per cent to between £700m and £750m, after M&S admitted that sales across all its divisions were suffering. The big downgrades came just weeks after Sir Stuart Rose, executive chairman, delivered £1bn in pre-tax profits for the year to March 31.