New Zealand is a constitutional monarchy. The constitutional authority in New Zealand functions at three different levels - parliament, the executive and the judiciary. New Zealand has no written constitution. The functions of government are set out under numerous Acts of Parliament, documents issued under the authority of the Queen, decisions of the court, relevant English and United Kingdom Acts of Parliament and unwritten constitutional conventions.
(Source: parliament.nz)
Parliament
The Parliament consists of the Sovereign and the House of Representatives. The members of Parliament are elected by people’s representatives for a term of three years. The power of dissolving Parliament and giving the Royal assent to bills passed in the House of Representatives rests with the Sovereign. The Parliament has only one chamber is unicameral.
Executive
Head of state
The Sovereign, Queen Elizabeth II of New Zealand is the head of state. The governor-general represents the Queen in New Zealand. The governor-general chairs the executive council and formally signs legislation into law after being passed by Parliament.
Government
Government is formed by the ministers of the crown or the cabinet who are the elected members of parliament. The prime minister is the leader of the governing party or coalition of parties holding the majority of seats in parliament and leads the cabinet.
The main political parties active in New Zealand are:
Regulatory environment
New Zealand enjoys a high degree of economic freedom in the Asia–Pacific region. New Zealand has experienced steady economic growth as a result of openness to global trade and investment. New Zealand withstood the recent global financial crisis due to the stable financial structure and regulated and controlled lending.
New Zealand supports the foreign and domestically owned business activities and to start a business in new Zealand only takes one day with few procedures in comparison to the world average of 35 days.
Business and economic freedom
New Zealand scored 82.1 on economic freedom index ranking it 4th freest economy in 2010.

(Source: heritage.org)
Corruption perception
New Zealand ranks 1st on the World’s Corruption Perception Index (CPI). CPI measures the perceived level of public-sector corruption in 180 countries and territories around the world.
(Source: transparency.org)
Freedom of information
New Zealand ranks 8th on the World press freedom index 2010 conducted by rsf.org.
New Zealand's press media is free from political parties and government involvement.
New Zealand Herald, Waikato Times, the Dominion Post, the Press, Otago Daily Times are key newspapers in New Zealand; while Television New Zealand, MediaWorks New Zealand, Sky Network Television and Freeview are some of the TV broadcasters.
(Source: rsf.org)
Judicial system
The judiciary in New Zealand is free from any political interference and has four levels
The Supreme Court is headed by the Chief Justice of New Zealand and is appointed on the advice of the prime minister. It is the final court of appeal in New Zealand. Appeals from the High Court are heard by the Court of Appeal. Criminal offences and civil matters and appeals from district courts are heard by the High Court.
(Source: parliament.nz, justice.govt.nz)