A Prime Minister is the head of government in a country with a parliamentary or semipresidential political system. In such systems, the head of state retains supreme executive power, but devolves substantial power into a cabinet led by a prime minister. Unlike some other senior positions, the prime minister is not appointed for an individual term and may remain in office through several elections and parliaments, as has happened in recent years with Margaret Thatcher (1979–90).
The prime minister’s role is to choose the MPs who will help him or her run the Government; these people are called cabinet ministers. The Prime Minister and his or her cabinet have to come up with lots of ideas about how to run the country. These are called policies. The prime minister and his or her cabinet have to work out how to get those policies put into action. The prime minister has to work with other heads of government to make decisions about things like international policy and defense.
In most countries with a parliamentary system, the prime minister is the leader of the political party that commands – either by itself or as the largest member of a coalition – a majority of seats in parliament. However, in some countries, the head of state appoints the prime minister of his or her choice: Examples include Ireland (the Taoiseach), Thailand and Japan.
The prime minister is expected to represent the interests of the country at home and on the world stage. To do this they need to keep the support of their own party members and the electorate. If they fail to do this they can face a leadership challenge or be forced out of office. Prime Ministers have to decide how to react when MPs oppose their Government. For example, they can remove the whip and force those MPs to vote with the Government, but this can have a long-term effect on the party’s support. The prime minister and his or her family live at 10 Downing Street. They are protected by armed police officers with “airport-style” security checkpoints, street patrols and heavy vetting for staff and non-ministerial guests.