Leading “Magic Circle” lawyers often fail to provide predictable and value-for-money bills, according to a poll of corporate clients, in a sign of tensions between the two sides as the credit crunch bites.

The five prestige firms – Clifford Chance, Linklaters, Freshfields Bruck­haus Deringer, Allen & Overy and Slaughter and May – all rank below average in a survey of more than 40 firms to be published by Legal Week magazine on Tuesday.