This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.This thesis examines the development of value for money (VFM) audit methods used by the National Audit Office (NAO) and considers what factors have influenced the identified changes. It also considers how developments compare with those elsewhere in Europe. The thesis is based on examination of more than 300 NAO reports,   interviews with senior staff, focus groups, a thorough review of relevant literature, and comparisons with four other state audit offices. The thesis argues that VFM audit has developed into a strong form of evaluative activity, despite a number of constraints. The NAO enjoys a unique combination of the statutory power to initiate wide-ranging reviews; the right to demand documents and gain access to people; and the existence of a powerful parliamentary committee to review its work and ensure a government response to reports. Additionally, during the 1980s and 1990s, the NAO developed its VFM work, and in particular, the methods used, to become a more robust discipline. Although document review and interviews form the basis of much of the work, other methods have been added to the core repertoire, in particular, questionnaires. In addition, a broader range of methods has been used on occasions, from focus groups to systems dynamics. These developments are explained in terms of a response to broader changes in the administrative environment, in particular, new  public management reforms. These have increased interest in public sector performance, enhanced the quality of information available, and given greater emphasis to service quality. Consequently, the NAO has sought to demonstrate it can 'add value' and encourage beneficial improvements to public services. Developments in methods are seen as one important way of doing this. The thesis places developments in the context of the growth of evaluative activities in the UK, whilst emphasising the particular focus of VFM work on accountability, and its links with financial audit.This work  was supported by the National Audit Office