Alastair Campbell, the former spin doctor to Tony Blair, has launched a provocative attack on George Osborne’s alleged preference for political tactics over economic credibility.

In a letter in Wednesday’s FT, Mr Campbell attempts to exploit City unease about the shadow chancellor’s perceived proclivity for headline-grabbing announcements. He cites as an example this week’s business backlash against Tory calls for an emergency cap on cash bank bonuses.