The backlash against Alistair Darling’s revenue-raising mini-Budget intensified on Wednesday when it emerged that thousands of employees participating in company “save as you earn” schemes could be landed with bigger tax bills.

As David Cameron, the Conservative leader, accused Gordon Brown of looking like “a phoney” and treating people “like fools” over his general election retreat, the wider effects of Labour’s sweeping tax changes became clearer, stoking business anger.