What does the prime minister do? Britain's head of government

The UK prime minister is the head of the government. What the prime minister does is lead it: choose the ministers who run each department, chair the Cabinet, set the government's priorities and answer for its decisions in Parliament. Voters don't elect the prime minister directly. The monarch appoints whoever can command the confidence of the House of Commons, which in practice means the leader of the largest party, and that person stays only as long as that support lasts.

In short

• The prime minister holds power because MPs back them, not because of a separate national vote.
• The role brings wide powers, from appointing ministers to deciding when to call an election, with few written limits.
• A prime minister can be replaced between elections, by their own party or by a vote of no confidence, and often has been.

How does someone become prime minister?

The prime minister's office is mostly a matter of convention, not statute. The government's own Cabinet Manual puts the rule in one line: the prime minister "holds that position by virtue of his or her ability to command the confidence of the House of Commons". By modern convention, the prime minister sits in the Commons, and is normally the leader of the party with a majority there.

So the path runs through a party and a seat. At a general election, voters in each of 650 constituencies elect one member of Parliament, and they vote for a local candidate, not for a prime minister. If one party wins a majority of the seats, more than 325, its leader is invited by the monarch to form a government and becomes prime minister at a private audience. If no party has a majority, a hung parliament, the leaders bargain: the 2010 election produced a coalition of two parties, and after 2017 a minority government survived through a deal with a smaller party.

What powers does the prime minister have?

Much of the power is formally the monarch's, under the royal prerogative, but the monarch acts on the prime minister's advice. In practice the prime minister:

• Appoints and dismisses ministers, including the Chancellor of the Exchequer and the Foreign, Home and Defence Secretaries, and decides how departments are organized.
• Chairs the Cabinet and its committees, sets its agenda and decides when a discussion is over.
• Sets the government's direction, from the King's Speech at the start of each session to the budget, which the prime minister agrees with the Chancellor.
• Leads on national security and foreign policy, including deploying the armed forces, signing treaties and representing the UK at summits.
• Recommends honours and some senior appointments, including new peerages in the House of Lords.
• Chooses when to call an election. Since the Dissolution and Calling of Parliament Act 2022, the prime minister can again ask the monarch to dissolve Parliament at any time, and a Parliament ends automatically five years after it first met.

The prime minister is also First Lord of the Treasury, by tradition, and Minister for the Civil Service. GOV.UK sums up the role as being "ultimately responsible for the policy and decisions of the government".

What limits the prime minister?

The prime minister's power is borrowed from the House of Commons, and the Commons can take it back. The limits are mostly political rather than legal.

• The Commons can withdraw confidence. A government that loses a vote of no confidence must win back the House's support or make way. The last time it happened, on 28 March 1979, James Callaghan's government lost by one vote, 311 to 310, and an election followed.
• Their own party can remove them. A prime minister is a party leader first. Each party has rules for challenging its leader, and a prime minister who loses the party's backing usually resigns.
• Parliament must pass the laws and the money. The government can't raise taxes or spend without the Commons' approval, and a rebellion by its own MPs can defeat a bill.
• Courts can rule actions unlawful. In 2019 the Supreme Court ruled that Boris Johnson's advice to prorogue, or suspend, Parliament for five weeks was unlawful, and Parliament returned.
• Elections, at least every five years.

Daily accountability happens in public. Every Wednesday that the Commons sits, the prime minister answers questions from MPs for about half an hour at Prime Minister's Questions, where the Leader of the Opposition gets six questions.

How can the prime minister change without an election?

Because the prime minister is whoever has the Commons' confidence, a party can change its leader, and so the country's prime minister, without a general election. The decade from 2016 shows how often that happens. The dates below come from GOV.UK's records and its page on the office; the 2026 leadership date is from The Conversation.

Year	Change	How it happened
2016	David Cameron to Theresa May	Cameron resigned after the EU referendum; May won the Conservative leadership
2019	Theresa May to Boris Johnson	May resigned over Brexit; Johnson won a Conservative members' ballot
2022	Boris Johnson to Liz Truss	Johnson resigned after his ministers quit; Truss won a members' ballot
2022	Liz Truss to Rishi Sunak	Truss resigned after about seven weeks; Sunak was the only nominee
2024	Rishi Sunak to Keir Starmer	Labour won the general election of 4 July 2024
2026	Keir Starmer to Andy Burnham	Labour changed leader: Burnham, back in the Commons after a by-election in June, was the only candidate, was confirmed as leader on 17 July and became prime minister on 20 July

Five of those six changes came without a general election. Some voters see that as a flaw: they feel they chose one leader and got another. Defenders of the system answer that voters elect a Parliament, not a person, and that a governing party's MPs replacing a leader they no longer trust is the system working as designed.

How is a prime minister different from a president?

	UK prime minister	US president
How chosen	Leader who commands the Commons' confidence	Elected nationally, through the Electoral College
Sits in the legislature	Yes, as an MP	No
Term	No fixed term; Parliament lasts up to five years	Fixed four-year term, at most two
How removed	Party leadership change or a no-confidence vote	Only by impeachment and conviction, or at an election
Head of state too	No, the monarch is head of state	Yes
Usual control of the legislature	Strong, since the government is the majority	Often faces a Congress controlled by the other party

A prime minister with a large majority can pass laws more easily than a US president, whose powers are deliberately split from Congress's. But a prime minister can also be removed far more easily. The note on parliamentary and presidential systems sets out the trade-off, which runs through democracies everywhere.

Still argued

Scholars and politicians have argued for decades about whether British government has become "presidential". One side points to prime ministers who run government from Downing Street, appeal to voters over their party's head, and dominate television debates during campaigns. The other points to how often prime ministers fall to their own MPs: Margaret Thatcher in 1990, Theresa May in 2019 and Boris Johnson in 2022, all while in office. Both trends can be true at once: the office has gathered more power, while the hold on it has stayed fragile.

Check yourself

• Without looking back: why does the leader of the largest party, rather than a winner of a national vote, become prime minister?
• Name three powers the prime minister uses through the monarch.
• How can a country get a new prime minister without holding an election?

Sources

• The Cabinet Manual — Cabinet Office, 2011
• Prime Minister — GOV.UK, 2026
• Past prime ministers — GOV.UK
• Dissolution and Calling of Parliament Act 2022 — legislation.gov.uk, 2022
• Andy Burnham is the Labour leader — The Conversation, 2026