The Parliament of Planets is the supreme legislative body of the United Imperial Worlds.  It is located in a large annex to the old United Nations Building in New York City, Earth.  The Parliament is composed of representatives from every Imperial world and every political party.  Normally, a ruling coalition is formed by non-majority parties and/or delegations from Imperial homeworlds. 

Representative Structure:  

Planetary Representation:  Every planet claims at least two seats.  More populous worlds may claim an additional seat for every 200 million individuals represented.  A series of two votes per individual determines the makeup of each planetary delegation.  Details...

Party Representation:  The first of two votes establishes the percentages of total seats per planets acquired by each party.  Thus, some planets are represented by one party only, while others may send representatives of every party.  Parties must claim at least 2% of votes overall to be included in the Parliament.

The two main parties are the Democratic Unionist Party (DUP) and their opposition, the Social Democratic Party (SDP).  Three smaller parties exist with which coalitions can be formed:  the Planetary Environmental Coalition (PEC), Imperial Industrialist Party (IIP), and Party for Planetary Autonomy (PPA).  The party system prevents populous planets from dominating the Parliament.  Details...

Individual Representation:  Individual candidates are elected with the second of two votes. Candidates are ranked by party according to votes received.  They are then placed into seats acquired by each party on each planet.  

Legislative Process:  Any member of the Parliament may submit a bill for consideration, although many of these are pigeonholed.  A majority of at least 51% is necessary to pass a bill, and any ties are broken by the Prime Minister.  The Parliament may also institute constitutional amendments, but in this case a 2/3 majority is necessary to become law.  Votes are most often divided along party lines, though voting by planetary delegation also occurs.

Power Structure:  The power of the Parliament of Planets is very great, as it forms a unicameral legislature.  Laws passed by the body are considered to supersede both planetary and local laws.  It maintains committees which oversee the actions of the Imperial Ministries, and votes to approve declarations of war and treaties.  However, two major checks on this power exist:  Laws may be ruled unconstitutional by the Imperial High Court of Justice, and tie-breaking votes are cast either by the Emperor or his appointed Prime Minister.