Prime ministers in parliamentary systems confront a challenging agency problem in leading cabinets toward cross-government priorities: ministers tend to prioritize departmental interests and may lack incentives and/or information enabling co-ordinated effort. In Canada, a novel mechanism for both increasing incentives and information provision has been developed in recent decades: the mandate letter. These letters are issued by Canadian prime ministers to their ministers, reinforcing government priorities, each minister's responsibilities, and specific policy expectations. This article examines mandate letters as mechanisms inducing interministerial policy co-ordination, focusing on the 2015–2021 period, under Justin Trudeau, as the first Canadian prime minister to release these letters publicly. Using topic modelling and social network analysis, I find that Trudeau has increasingly sought to strengthen ministerial co-ordination and ministers’ focus on crosscutting policy priorities. This case study contributes to our understanding of intraexecutive co-ordination and the agency problem in cabinet government.
