Parliament is made up of two chambers. The lower house, the House of Commons, is made up of 650 Members of Parliament, who each represent an area of the country (known as constituencies). A general election, whereby all 650 MPs are elected at once, must be held no later than five years after previous general election.

These five years are somewhat confusingly known as ‘a parliament’. If an MP leaves office for whatever reason before the next general election, a by-election is held in their constituency. MPs are split into three groups.

The party (or parties) of government. These are the MPs who belong to a political party which makes up His Majesty’s Government (often referred to as simply the Government). Whilst theoretically anyone can become Prime Minister, it is by tradition the person who leads the largest party in the House of Commons who is appointed by the King and asked to form a government.

This is because the government needs to be able to secure a vote from the majority of MPs. If more than half of MPs vote to oust the government, then a new government must be formed which can gain the House’s support, or a general election must be called. The second largest party forms His Majesty’s Most Loyal Opposition (often referred to as simply the Opposition).

The party leader becomes Leader of the Opposition, and also leads the Shadow Cabinet who critique the government’s policy. The idea of the Opposition is to act as a government-in-waiting. Being the Official Opposition grants privileges to the party, most notably more time during debates to scrutinise the Government.

This is most often seen at Prime Minister’s Questions where the Leader of the Opposition is given six questions, whilst the leader of the third largest party (currently the Liberal Democrats) is granted two. No other Member of Parliament is guaranteed to receive any questions. The upper house of the UK Parliament is the House of Lords.

The House of Lords currently consists of 804 members. It is the second largest legislative body in the world, and the only upper house larger than the lower. There are three types of members in the House of Lords.

The largest group are the 687 appointed by the King, on the advice of the Prime Minister, to life peerages, meaning they serve in the House of Lords for the period of their lifetime. Another 92 are hereditary peers, meaning that their membership of the House of Lords is passed down through the generations of their family. Collectively, the appointed and hereditary peers are known as ‘Lords Temporal’.

It is important to note that the current government has pledged to abolish the hereditary peers, and mandate that peers retire at 80. The third type of peer, known as ‘Lords Spiritual’ are bishops from the Church of England, their number is capped at 26. Bills (prospective laws) require the approval of both houses to become law.

A bill can be proposed in either house and works its way through both in much the same way. One of the reasons that there are so many members of the House of Lords is that the government requires any legislation to also pass that House. While the government will almost always have a majority in the Commons, this is not guaranteed in the Lords where there are no elections.

As such, Prime Ministers appoint new peers to shore up their numbers. Currently, for example, whilst there is a Labour government, in the upper chamber only 185 Lords are members of the Labour Party. Successive Prime Ministers have been criticised for appointing political cronies to the Lords as opposed to experts and people deserving of a peerage.

There are a number of factors which means that the House of Commons is the dominant chamber. Firstly, the Salisbury Convention is an understanding that any pledge mentioned in a government’s pre-election manifesto will not be opposed by the Lords. Secondly, the Parliament Acts of 1911 and 1949 prevent the House of Lords from vetoing most legislation that passes the House of Commons.

Under the 1949 Act, any legislation that is passed by the House of Commons which the Lords refuses to pass, can be passed into law regardless, if the Commons votes for it again after a year. This power is rarely used by the Commons (it has been twenty years since the last time) but it cements the dominance of the elected chamber and reduces the Lords to being primarily a chamber for (in theory) apolitical legislative scrutiny.