Australian Government/The Commonwealth Legislature
The legislature of the Commonwealth is the Commonwealth Parliament or Parliament of Australia. The Parliament of Australia is a bicameral parliament consisting of the House of Representatives (the "lower house") and the Senate (the "upper house" or "house of review"). Section 1 of the Constitution of Australia provides that: "The legislative power of the Commonwealth shall be vested in a Federal Parliament, which shall consist of the Queen, a Senate, and a House of Representatives, and which is herein-after called 'The Parliament,' or 'The Parliament of the Commonwealth'."
Queen Elizabeth II is, in her capacity as Queen of Australia, Australia's head of state, but her constitutional functions in Australia are delegated to the Governor-General of Australia.
The House of Representatives consists of 150 members elected from single-member constituencies of approximately equal population. The Senate consists of 76 members: 12 Senators are elected from each of the six states and two from each of the two territories.
The principal function of the Parliament is to pass laws, or legislation. Any Member or Senator may introduce a proposed law (a bill), except for a money bill (a bill proposing an expenditure or levying a tax), which must be introduced in the House of Representatives. In practice, the great majority of bills are introduced by ministers. Bills introduced by other Members are called private members' bills. All bills must be passed by both Houses to become law. The Senate has the same legislative powers as the House, except that it may not amend money bills, only pass or reject them.
The Parliament performs other functions besides legislation. It can discuss urgency motions or matters of public importance: these provide a forum for debates on public policy matters. Members can move motions of censure against the government or against individual ministers. On most sitting days in both Houses there is a session called Question Time at which Members and Senators address questions to the Prime Minister and other ministers. Members and Senators can also present petitions from their constituents. Both Houses have an extensive system of committees in which draft bills are debated, evidence is taken and public servants are questioned.
Members of the Australian Parliament do not have legal immunity: they can be arrested and tried for any offence. They do, however, have Parliamentary privilege: they cannot be sued for anything they say about each other or about persons outside the Parliament. This privilege extends to reporting in the media of anything a Member or Senator says.
There is a legal offence called contempt of Parliament. A person who speaks or acts in a manner contemptuous of the Parliament or its members can be tried and, if convicted, imprisoned. The Parliament used to have the power of hearing such cases itself, and did so in the Browne-Fitzpatrick case of 1955. This power has now been delegated to the courts, but no-one has been prosecuted for this offence.
The House of Representatives 
The 150 members of the house are elected from single-member geographic districts (popularly known as "seats" but officially known as "Commonwealth Electoral Divisions") which are intended to represent reasonably contiguous regions, with relatively equal population in each of about 80 000 people. Voting is by the preferential system.
According to Australia's Constitution, the powers of both houses are nearly equal with the consent of both houses needed to pass legislation. In practice, however, the Lower House is far stronger in some ways, and far weaker in others.
By convention, the party or coalition in the lower house with a majority is invited by the Governor-General to form government, and thus the leader of the party in the lower house becomes the Prime Minister of Australia and his senior colleagues ministers responsible for various government departments. Bills appropriating money can also only be introduced or modified in the lower house. Thus, only parties in the lower house can govern. However, in the rigid Australian party system, this ensures that virtually all contentious votes are along party lines, and the government always has a majority in those votes. The Opposition's only real role in the House is to present arguments why the government's policies and legislation are wrong, and attempt to embarrass the government as much as possible by asking difficult questions at question time.
In a reflection of the color scheme of the United Kingdom House of Commons, the House of Representatives is decorated in green.
The Senate 
The voting system for the Senate has changed twice since it was created. The original arrangement was a first past the post block voting mechanism. In 1919, it was changed to preferential block voting. Block voting tended to grant landslide majorities very easily. In 1946, the Australian Labor Party government won 30 out of the 33 Senate seats. In 1948, partially in response to this extreme situation, they introduced proportional representation in the Senate.
From a comparative governmental perspective, the Australian Senate is almost unique in that unlike the upper house in other Westminster system governments, the Senate is not a vestigial body with limited legislative power but rather plays and is intended to play an active role in legislation. Rather than being modelled after the House of Lords the Australian Senate was in part modelled after the United States Senate and was intended to give small rural states added voice in a Federal legislature, while also fulfilling the revising role of an upper house in the Westminster system.
Although the Prime Minister is answerable to, and selected from the House of Representatives (the "lower house"), other ministers are drawn from either house and the two houses have almost equal legislative power. As with most upper chambers in bicameral parliaments, it cannot introduce Appropriation Bills or impose taxation, that role being reserved for the universally elected lower chamber. That degree of equality between the Australian Senate and House of Representatives is in part due to the age of the Australian constitution; it was enacted before the confrontation in 1909 between the British House of Commons and House of Lords, over estate taxes, which ultimately resulted in the restrictions in the powers of the House of Lords in the Parliament Act. The Senate thus reflected the pre-1911 Lords-Commons relationship, namely a house with theoretically wide powers that are by convention not widely used, but which in a crisis could be.
However in one area it possesses a highly sensitive power, namely the right to withdraw or block Supply, i.e. government control of exchequer funding. In most democracies, this power does not exist within upper houses. In the Australian case, probably due to its age and its pre-dating of the British Parliament Act, 1911, that power, once possessed by the House of Lords, is still possessed by the Australian Senate. What it means is that in strict constitutional terms, the Government is also answerable to the Australian Senate, given that the loss of Supply in parliamentary democracies automatically requires the resignation of a government or ministry, or alternatively the calling of a general election, because without access to exchequer funding a government cannot function and would face bankruptcy. However, as in the United Kingdom prior to the 1909 clash over David Lloyd George's budget between the House of Commons and House of Lords, a general convention built up in which the upper house would not use its power to block exchequer funding, leaving that responsibility to the democratically representative lower house. Indeed to break convention in this area is sometimes described as a parliamentary nuclear option because of its political, financial and governmental impact. In 1975, in a dispute strikingly similar to Britain's 1909 clash (an upper House breaking convention by withdrawing Supply on the basis that it was reacting to a breach of another fundamental convention by the government - which the government denied) the Senate did refuse to pass a required financial measure, producing a 'nuclear'-style crisis which resulted in a stand off, a decision of the Prime Minister not to resign or seek a dissolution, and the eventual intervention of the Governor-General to withdraw the commission of the Australian Prime Minister (in effect dismissing him) and the appointment of a minority government from the opposition in the House of Representatives and the calling of a general election.
In practice, however, most legislation (except for "Private Member's Bills") in the Australian Parliament is initiated by the Government, which has control over the lower house. It is then passed to the Senate, which may amend the bill or refuse to pass it. In the majority of cases, voting is along party lines.