Victor van Wetering, former editor of gay newspaper Express, first complained to the Human Rights Commission about the exclusion, which he called "actively discriminatory", in 2001.
Mr van Wetering and the Office of Human Rights Proceedings, the independent legal branch of the commission, expect to discuss the inclusion of the question in the 2011 Census with lawyers for Statistics New Zealand later this year.
Mr van Wetering said a question on sexual orientation would provide policy makers and planners with useful information to serve the gay community.
"For example, some public campaigns might become more targeted at queer New Zealanders if this group was found more likely to smoke, or less aware of benefit entitlements, than other New Zealanders."
In 2003, Statistics New Zealand research indicated most people would accept or grudgingly accept such a question, provided people could refuse to answer.
It is illegal under the Human Rights Act for a government policy to treat any section of the community unfavourably due to their sexual orientation.