Civil union has been legal in New Zealand since 26 April 2005. The Civil Union Act 2004 to establish the institution of civil union for same-sex and opposite-sex couples was passed by the Parliament on 9 December 2004. The Act has been described as very similar to the Marriage Act 1955 with references to "marriage" replaced by "civil union". A companion bill, the Relationships (Statutory References) Act, was passed shortly thereafter on 15 March 2005, to remove discriminatory provisions on the basis of relationship status from a range of statutes and regulations. As a result of these bills, all couples in New Zealand, whether married, in a civil union, or in a de facto partnership, now generally enjoy the same rights and undertake the same obligations. These rights extend to immigration, next-of-kin status, social welfare, matrimonial property and other areas. Non-married couples are not however permitted to adopt children, although people in non-marital relationships can adopt as individuals.
Both the Civil Union Bill and the Relationships (Statutory References) Bill were promoted as part of their Ministerial responsibilities by the Labour MPs and Ministers David Benson-Pope and Lianne Dalziel. The Civil Union Bill was treated as a conscience issue by most parties, including the largest parties on the left and right, and passed its third and final reading by 65 votes to 55.
During consideration of the bill, various amendments were proposed. These included making the issue subject to a binding referendum, (a motion moved by New Zealand First MP Ron Mark who voted for the first two readings of the Bill, but against in its final vote). Another was to replace it with a "civil relationships" bill that would allow any two people to register any personal relationship and to gain joint property rights (moved by National MP Richard Worth, a consistent opponent of the bill). These proposals were dismissed by supporters of the bill as delaying tactics rather than serious proposals and were defeated in Parliament by a block vote of Labour, the Greens, and the Progressives.