Partnership working is nowadays a seemingly ubiquitous aspect of the management and delivery of public services, yet there remain major differences of opinion about how they best work for the different stakeholders they involve. The balances between mandate and trust, and between hard and soft power, are crucial to current debates about public service partnerships. This paper explores the example of social housing procurement in Northern Ireland, and the requirement to form mandated procurement groups. The research shows that the exercise of hierarchical power is still important in network governance; that mandated partnerships alter the balance between trust and power in partnership working, but the impact is uneven; and that these relationships are (re)shaping the ‘hybrid’ identity of housing associations. The balance between accountability for public resources and the independence of third sector organisations is the key tension in mandated partnerships. The Northern Ireland experience suggests that trust-based networks could provide more productive working relationships in partnerships for service delivery.