The investment and mortgage policies and practices of the British building societies affect individuals, neighbourhoods and the economy. Their activities have been subject to serious criticisms. Building societies, however, are scarcely accountable to their members, despite their position as‘mutual’ organizations; nor are they politically accountable to the electors through the government. The British building societies present a public interest problem. This article questions whether and how they ought to be made accountable for their actions in order to ensure that they further the public interest.