The role of public relations in civil society and the degree to which public relations work exerts influence on the shape and texture of public discourse in democratic societies is a contentious issue. While public relations has grown to be a significant industry in terms of revenue and employment, it continues to attract public criticism; and the related academic discipline, with its well developed body of knowledge, receives general low regard as a field of professional practice.  Through a critical discourse analysis of Australia’s pneumococcal communication campaign and its media coverage between 2001 to 2004, this study explores the role and influence of public relations in the construction of public discourse. Current understandings of the social role of public relations are traced, pointing out the lack of consensus in the literature on an appropriate articulation of the relationship between public relations and the public interest. Conceptualisations of an effective public sphere are reviewed and a perspective which draws on the work of Habermas, Foucault and Bourdieu is proposed as a means by which media discourse may be examined. The assumption underpinning this study is that one of the reasons for the negative perception of public relations is its failure to articulate its social role: that is, how PR power is enacted in the public interest.  The study reveals the complexity of public relations discourses and the pervasiveness of their influence. It also reveals the complex relationships between discourse actors seeking to enact their interests in political debate in the public sphere The importance of ethical and accountable practices to both the reputation and development of public relations as a profession are highlighted. The analysis of the discourse practices of PR enacted in the public sphere reveals a misuse of power and a distortion of public debate.  The study finds that public relations professionals have a major role to play in discourses concerning the creation and maintenance of civil society. As well as communicating the strategic intents of their clients, public relations needs to a professional ideology which recognises their role in multiple public spheres and take part in debates on issues of concern to the profession. There must also be clear acknowledgement and articulation of the wider social role played by public relations. Deeper appreciation of this role and its implications for the shaping of civil society strengthens the imperative for practitioners to understand and enact ethical behaviour