In this age of local autonomy, collaborative relationships between central and local governments are emerging as an important policy agenda. However, central government still sustain vertical relationships with local government in practices and this leads to frequent conflicts in the national policy implementation process. Fortunately, the current regime has adopted the local autonomy and balanced national development as one of key policy agenda among 5 key policy directions and 20 major policy strategies at the national level. The objective of this research was to suggest more collaborative policy tools and mechanisms to enhance the role of the local government as the policy counterpart of the central governments through active participations in the national policy making process. This research proceeds to thoroughly review related model research documents and actual cases studies of conflicts with central government in the national policy projects to establish the status of local government involvement in the national policy affairs. Infant and young children free care project and young people activity support project of the Seoul Metropolitan Government were investigated as case studies of conflicts between central and local governments in the national policy affairs. Subsequently, an in-depth examination of four advanced policy tools and mechanisms for collaborative inter-governmental relations at home and abroad were conducted including: collaborative council between central and local governments in Japan as a group consultative mechanism; horizontal administrative agreement cases between central and different local governments in England; case of the Unfunded Mandate Reform Act in USA; and local autonomy impact assessment case of the Seoul Metropolitan Government in Korea. Additionally, e-mail surveys of experts who have some experiences in the national policy projects were conducted to establish experts’ perceptions and opinions in regards to the relationships between local and central governments and the suitability of various policy tools and mechanisms currently in use.   
Major policy implications of this research are as follows; First, despite of the existence of various co-operative policy tools, some centralized authoritarian rules and practices are still in place making local governments participation in the national policy affairs arbitrary and passive in reality. Second, co-operative group consultation mechanism between the central and local governments seem to be the most applicable to the Korean situation. In spite of good motives and some merits, administrative agreements between the central and individual local governments have numerous limitations and consider undeveloped policy tools for local governments in Korea with the exception of Seoul Metropolitan Government. The survey results also confirm that the relationships between the central and local governments are perceived as vertical and sub-ordinate for majority of experts in related fields. There’s emphasis on the importance of solid legal base for a more collaborative inter-governmental relations and consultative mechanism between central and local government. According to the previous discussions, this research suggest that legislations of more solid local autonomy are required as pre-conditions of collaborative and horizontal inter-governmental relations. However, phased adaptive strategies are also proposed for the transition period considering the expected challenges of proper legislations in the present situation. Therefore, despite issue points based specific improvements of various current policy tools for the co-operative inter-governmental relations are immediately suggested as the policy priority. Setting up of a collaborative council consisting of some representatives from the central governments and local governments is suggested as the new institutional consultative mechanism at the national level. Similarly, for some specific public service areas, horizontal administrative agreements between the central and individual local governments need to be seriously considered as a co-operative consultative policy tools in national policy projects. This policy tool seems useful especially for the individual local governments having enough administrative capacity, such as the Seoul Metropolitan Government.