The politics of New Zealand function within a framework of a unitary parliamentary representative democracy. New Zealand is a constitutional monarchy in which a hereditary monarch—since 6 February 1952, Queen Elizabeth II—is the sovereign and head of state.
Executive power in New Zealand is based on the principle that "The Queen reigns, but the government rules". The Prime Minister is the highest government minister, chair of the Cabinet and head of government, holding office on commission from the Governor-General of New Zealand. The office of prime minister is, in practice, the most powerful political office in New Zealand. Government ministers are selected from the elected members of the New Zealand Parliament.
The country has a multi-party system in which many of its legislative practices derive from the unwritten conventions of and precedents set by the United Kingdom's Westminster Parliament. However, New Zealand has evolved variations; minority governments are common and typically dependent on confidence and supply agreements with other parties. The two dominant political parties in New Zealand have historically been the New Zealand Labour Party and the New Zealand National Party (or its predecessors).