Parliament system of the United Kingdom

The Parliament of the United Kingdom of Great Britain and Northern Ireland, commonly known as the UK Parliament or the British Parliament, is the supreme legislative body in the United Kingdom, British Crown dependencies and British overseas territories. It alone possesses legislative supremacy and thereby ultimate power over all other political bodies in the UK and its territories. Its head is the Sovereign of the United Kingdom (currently Queen Elizabeth II) and its seat is the Palace of Westminster in Westminster, London.

The parliament is bicameral, consisting of an upper house (the House of Lords) and a lower house (the House of Commons). The Sovereign forms the third component of the legislature (the Queen-in-Parliament).The House of Lords includes two different types of members: the Lords Spiritual (the senior bishops of the Church of England) and the Lords Temporal (members of the Peerage) whose members are not elected by the population at large, but are appointed by the Sovereign on the advice of the Prime Minister. Prior to the opening of the Supreme Court in October 2009, the House of Lords also performed a judicial role through the Law Lords.

The House of Commons is a democratically elected chamber with elections held at least every five years. The two Houses meet in separate chambers in the Palace of Westminster (commonly known as the Houses of Parliament) in London. By constitutional convention, all government ministers, including the Prime Minister, are members of the House of Commons – or, less commonly, the House of Lords – and are thereby accountable to the respective branches of the legislature.

The Parliament of Great Britain was formed in 1707 following the ratification of the Treaty of Union by Acts of Union passed by the Parliament of England and the Parliament of Scotland. At the start of the nineteenth century, Parliament was further enlarged by Acts of Union ratified by the Parliament of Great Britain and the Parliament of Ireland that abolished the latter and added 100 Irish MPs and 32 Lords to the former to create the Parliament of the United Kingdom of Great Britain and Ireland. The Royal and Parliamentary Titles Act 1927 formally amended the name to the "Parliament of the United Kingdom of Great Britain and Northern Ireland", 5 years after the secession of the Irish Free State.

The UK parliament and its institutions have set the patterns for many democracies throughout the world, and it has been called "the mother of parliaments".However, John Bright – who coined the epithet – used it with reference to a country (England) rather than a parliament.

In theory, the UK's supreme legislative power is vested in the Crown-in-Parliament. As, however, the crown acts on the advice of the Prime Minister and the powers of the House of Lords have been curtailed, de facto power is vested in the House of Commons.