As the leader of the government and ultimate responsible for government policy, the Prime Minister has a unique responsibility. The Prime Minister and Cabinet are ultimately accountable to Parliament for their actions, successes and failures. The Prime Minister sets the broad organisational structure of departments and the relationships between them through mandate letters, and allocates responsibilities to ministers by allocating portfolios. Ministers and their officials are accountable for the actions of their departments and agencies to Parliament and the Prime Minister through regular reports.

The Prime Minister must ensure that enough MPs support their decisions for the government to function, and keep its majority in the House of Commons. This requires political crisis management and the ability to motivate MPs in a time of uncertainty. A Prime Minister must consider the effect of any decision they make on their own party and constituents, as well as the wider community.

The PM must decide on policies that will help the UK to achieve its aims and ambitions. They must then create a team of people who can work together to put those policies into action. The Prime Minister and the rest of the cabinet must be able to share collective responsibility for decisions, even ones they do not individually agree with.

The Prime Minister must represent the government on a domestic and international level, to politicians and other heads of state and supranational organisations. This includes delivering speeches at times of national mourning and emergencies. The Prime Minister must also communicate with the media and citizens to explain any issues that affect them.