The role of the prosecuting lawyer, despite its crucial importance in the administration of criminal justice, has often been both misunderstood and overlooked. The prosecutor acts not as a partisan advocate bent solely on the conviction of the accused but rather as the disinterested minister of justice whose only purpose is to assist the court in arriving at the truth of the matter in dispute and promoting justice. This notion is deeply entrenched in the criminal law. This Thesis considers the development of the prosecutorial role in England and Australia as a minister of justice. It examines specifically the development and application in England and Australia of two important functions performed by the prosecution; first, the prosecution's obligations in the disclosure of relevant material in its possession to the defence and, secondly, the prosecution's discretion in its choice of the witnesses to call at trial. The focus of this Thesis is on the performance of these two functions in the context of the preparation for trial and/or the conduct of a criminal trial on indictment before the higher courts. This Thesis considers the inherent tension in the exercise of these functions between the dual prosecutorial roles of minister of justice and active advocate in an adversarial criminal justice system. It is argued that this tension is ultimately not capable of reconciliation. This Thesis questions the extent to which the minister of justice concept remains an appropriate model to govern the exercise of the modern prosecutorial role. It is argued that more than rhetoric is necessary to define and govern the modern prosecutorial role adequately. It may be timely to reconsider the minister of justice concept as a universal definition of the modern prosecutorial role. It is accepted that in relation to disclosure of relevant material the prosecution must act as the candid minister of justice. However, it is argued that the prosecuting lawyer should be free with respect to some functions and in some circumstances to assume a robust and adversarial‚ÄövÑvp role, notably with regard to its choice of the witnesses to call at trial.