Nearly 50 people have been turned down as marriage celebrants because they refuse to solemnise same-sex marriages.
The Department of Internal Affairs said 47 applications to become independent celebrants had been turned down since 2015.
The Registrar of Births, Deaths, and Marriages, Jeff Montgomery said celebrants affliated with a religious or philisophical organisation could choose who they offered their services to.
But independent marriage celebrants provided a service on behalf of the government, rather than an organisation, he said.
That meant they must comply with all the relevant laws, including the Human Rights Act, which makes it an offence to discriminate based on sexuality.
The number of declined applications was a small proportion of the 500 people who apply each year to become celebrants, Mr Montgomery said.