What jobs do Prime Ministers do?
In most systems, the prime minister is the presiding member and chairman of the cabinet. In a minority of systems, notably in semi-presidential systems of government, a prime minister is the official who is appointed to manage the civil service and execute the directives of the head of state.
The Prime Minister is the leader of Her Majesty's Government and is ultimately responsible for the policy and decisions of the government. As leader of the UK government the Prime Minister also: oversees the operation of the Civil Service and government agencies. appoints members of the government
The prime minister is the leader of the government and is appointed by the Queen. Normally, he or she is the leader of the party that wins a general election.
And the prime minister can also bring in new laws - so long as they receive the backing of Parliament.
Ultimately, the prime minister is responsible for all government policy and decisions. Alongside the chancellor, the prime minister is also in charge of tax-and-spending policy.
What other powers do they have?
The prime minister has overall control of the civil service - the people and departments that carry out the government's decisions.
They can award honours, such as knighthoods and damehoods. They can also award peerages.
They also have a number of responsibilities relating to defence and security.
For example, they have the power to send the UK's armed forces into action. However, recent convention says Parliament should also approve such a decision.
A number of special responsibilities also rest on the prime minister's shoulders, such as deciding whether to shoot down a hijacked or unidentified aircraft.
How are prime minister held to account?
Despite these powers, a prime minister can't just take any decision they like.
Prime ministers need to retain the confidence of most MPs. That's because laws can only be passed if a majority of MPs vote them through.
If a government repeatedly loses votes, MPs could choose to call a "motion of no confidence". If a prime minister loses such a vote, they face the prospect of a general election.
If the prime minister's party loses a general election, they must resign so the leader of the winning party can take over.
In theory, the Queen has the power to sack a prime minister if it was felt they were acting against the country's interest. That, however, would trigger a constitutional crisis.
Who gets to choose the prime minister?
Boris Johnson needed the backing of both Conservative MPs and ordinary party members.
To start with, 10 Tory MPs were nominated as possible prime ministers. But a series of secret votes by Conservative MPs whittled them down to two - Boris Johnson and Jeremy Hunt.
Both Mr Johnson and Mr Hunt took part in a series of debates, before paid-up members of the Tory Party voted for who they wanted.
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