Lazard, the investment bank advising corporate raider Carl Icahn on his campaign to break up Time Warner, last night said shareholders have lost at least $40bn (€33bn) in value from mis-management of the US media conglomerate and recommended a four-way split of the group.

Icahn hired Lazard in November as part of his bid to force a break-up of Time Warner and has carried out an in-depth study that Bruce Wasserstein, chairman and chief executive of Lazard, presented today.