Multi-agency collaboration is often advocated as a means of tackling cross-cutting areas of public services and viewed as a solution to service fragmentation, with local agencies on the receiving end of government exhortations to collaborate.  Yet there is relatively little research examining the effectiveness of policy tools and mechanisms aiming to stimulate local collaboration. This thesis examines the influence and dynamics of vertical and horizontal coordination tools, investigating their potential to enhance collaboration in local public service delivery networks and to reduce negative externalities.  A theoretical framework is employed which synthesises models of policy implementation and bureaucratic decision-making. The empirical research is conducted in relation to organisations working with the homeless in England, and the research methods include a survey of Local Authorities and interviews with civil servants and frontline professionals.  While governmental attempts to foster collaboration are partially effective, there are weaknesses with some of the policy tools employed, and limits to State control.  Local actorsâ\u80\u99 collaborative decision-making is influenced more by â\u80\u98bottom-upâ\u80\u99 than by â\u80\u98top-downâ\u80\u99 factors.  Moreover, the competitive context in which service providers operate leads them to pursue strategies to promote their own organisational interests rather than working towards a dominant common interest.  The strategies employed are broadly in line with a bureaucratic politics perspective, and include failure to share information, possessiveness over client outcomes and projecting an image of success rather than sharing problems.  Nevertheless, formal collaborative mechanisms do have the potential to alleviate externalities associated with fragmented systems. With strong local management and appropriate central facilitation, they can help to meet client needs and to counter fragmentation, ultimately leading to better services.Economic and Social Research Council/ Office of the Deputy Prime Minister/ Price Waterhouse Cooper