As a consequence of a popular referendum held in June 1995, the provision stating legal criteria for the determination of repte-sentative trade unions entitled to negotiate collective agreements in the public sector (Art. 47 d.lgs. 29/1993) has been repealed. The Author deems this legal vacuum could be filled by way of in-terpretation, throught an application of principies and categories drawn from administrative law. The paper analyses therefore the prerogatives of the Government and of the Agency for Bargaining Representation (a new institution set up in order to represent the public counterpart in the collective bargaining rounds), referring also to the rules governing the private contracts signed by the pu-blic administration for the purchasing of goods and services.