What Does a Prime Minister Do? Power Without a Job Description
By the BrainSnail editorial team. How these articles are written and checked, and how to tell us when one is wrong.
In Britain the office is not created by any statute, its powers are nowhere written down in full, and for most of its history the holder's authority rested on convention, patronage and the ability to keep a majority. The first person generally counted as holding it did not use the title, which was originally an insult meaning that one minister had improperly made himself superior to the others. Parliamentary systems across the world now run on the office, and what it can actually do varies enormously.
How the office works
A prime minister is the head of government, distinct from a head of state who may be a monarch or a ceremonial president, and holds office by commanding the confidence of the legislature rather than by winning a separate election. That single fact drives everything else:
- •Appointment follows from being able to command a majority, so the head of state's role in appointing is normally formal, and becomes real only in a hung parliament
- •The holder can be removed at any time by losing a confidence vote, or, more commonly in practice, by losing the support of their own party
- •They are usually a member of the legislature and answerable to it directly, which is why parliamentary questions exist and why a presidential system has no equivalent
- •They appoint and dismiss ministers, which is the largest single source of internal authority, since every ambitious colleague depends on it
- •They chair the cabinet, control its agenda and decide what is discussed, which shapes collective decisions more than any vote within it
- •They usually decide when to call an election, within limits, which is a considerable tactical advantage and has been restricted by statute in several countries
The British case and its oddities
The office emerged rather than being designed. Robert Walpole, in post from 1721 to 1742, is conventionally counted as the first, at a period when a German-speaking king took a diminished role in cabinet and one minister came to coordinate it. The title had no legal recognition until 1905 and appears in statute only incidentally. Much of the power exercised is prerogative power, historically belonging to the Crown and now exercised by ministers, covering the deployment of armed forces, the making of treaties, the granting of honours and the appointment of senior officials, none of which requires a statute. The constraints are correspondingly informal: the convention of collective responsibility, which requires ministers to support decisions publicly or resign, the need to retain the confidence of the parliamentary party, and the electorate. Several recent episodes have tested whether informal constraints suffice, including the 2019 prorogation of Parliament, which the Supreme Court held unlawful, and the removal of two prime ministers by their own party within months in 2022.
How much power is real
The long argument in British political science is whether cabinet government has been replaced by something closer to a presidency. The case for that reading points to the growth of the prime minister's own staff and policy units, the personalisation of election campaigns around leaders, direct communication with the public that bypasses cabinet, the dominance of a small group of senior colleagues over formal cabinet meetings, and the centralisation of media management. The case against points out that the holder has no department of their own, very few statutory powers, depends entirely on party support that can evaporate quickly, and can be removed in a week by a few dozen colleagues, which no president faces. The reasonable summary is that the office is powerful when the holder is electorally successful and united behind, and extraordinarily weak when they are not, so the same constitutional position produces very different amounts of actual authority depending on circumstances that have nothing to do with law.
Variation across systems
The office differs substantially between countries with the same basic design. Germany's chancellor is unusually secure, because the constitution requires a constructive vote of no confidence, meaning the parliament cannot remove a chancellor without simultaneously electing a successor, which was written specifically to avoid the instability of the Weimar Republic. Italy's prime minister has historically been weak, with governments averaging little over a year since 1946. In coalition systems such as the Netherlands, Belgium and much of Scandinavia, the holder is a negotiator between parties whose agreement is set out in a written coalition document, rather than a leader with a mandate of their own. Semi-presidential systems including France and Russia place a prime minister alongside a directly elected president, and the balance between them shifts with who controls the legislature, producing periods of cohabitation in which the two come from opposing parties. Israel, Japan and India each add their own variations. In every case the written rules explain less than the party system does.
The takeaway
A prime minister heads a government and holds office by commanding the confidence of the legislature rather than through a separate election, which makes the power to appoint and dismiss ministers, chair the cabinet and set its agenda the practical sources of authority. The British office grew by convention from Walpole onwards, has almost no statutory basis, and exercises prerogative powers over armed forces, treaties and appointments. Its real strength depends on party support rather than law, and constitutional variants from Germany's constructive no confidence vote to French cohabitation produce very different offices.