With the financial crisis, it becomes more and more difficult and expensive to obtain funding for infrastructure projects. Public sector procurement is undergoing major changes. Drastic cuts in government budgets re-ignited the debate of centralisation versus decentralisation that was last debated after the oil crisis of 1973. In the traditional marketing and purchasing literature, the relationship between Buyer and Seller has long been at the centre of the purchase interaction. Organisations have chosen close long-term relationships instead of “playing the market” in the name of cost reduction and increased revenues. The objective of this study is to identify the particular constraints on relationship building in the public sector, and to assess whether or not these constraints make standard efficient management practices inapplicable to the public sector. Several organisations from the Irish public sector were interviewed about their relationships. The qualitative data collected from the interviews were combined with the current related literature of business to business relationships, public procurement and organisational buying behaviours. It is argued in this research that it is extremely difficult to establish a collaborative relationship with suppliers when mandatory rules and procedures create formal and centralised buying behaviours. In conclusion, lessons for developing collaborative arrangements in public procurement are identified.