The policy has incensed a Wellington man, who says it is unjustified discrimination. Experts agree the policy breaches human rights and others say it should be reviewed, given the donor shortage and improved HIV testing regimes.
The sperm shortage is such that women are waiting up to two years for a donor, and some have been told to find their own.
Hearing of the situation, the man - who would not be named - rang Wellington's Fertility Associates clinic to sign up with his long-term partner. He was appalled the second question he was asked was "Are you heterosexual?". When he said he was gay, he was told he could not donate.
"I said that was extremely prejudiced and asked her why, but she couldn't tell me."
Fertility Associates medical director John Hutton said his clinic was only following the rules, set down by the Health Ministry.
All New Zealand fertility clinics have to be accredited by the Reproductive Technology Accreditation Committee, which requires donors to complete a lifestyle and medical history declaration designed to minimise the risk of passing on an infectious disease.
Though all sperm was screened for HIV and other diseases, homosexual men were a higher risk group and were therefore excluded, along with intravenous drug users, Professor Hutton said.
The policy aimed to reduce infection risk and was not a moral judgment, or based on fears that homosexual genes could be passed on, he said.
Gay men could still donate if the receiving woman or couple sought them out (often the case with lesbian couples) and were prepared to take the risk. Sexually-active homosexual men are also prohibited from giving blood, despite the fact the Blood Service's own information booklet acknowledges that an increasing number of New Zealanders diagnosed with HIV are infected through heterosexual contact.
A Christchurch woman has had five children with her partner, using sperm from a gay friend. Excluding gay men from sperm banks was ridiculous, even for medical reasons, she said. HIV could affect anyone and it was ignorant to believe gay men were all engaging in risky sex, while straight men were not.
"Most women who require donor treatments have to wait so long they are just so grateful when they get it, because it is such a great gift. They expect it to be safe but they don't expect further delay through ignorance and discrimination."
Wellington lawyer Tony Ellis said the policy was blatant and irrational discrimination, resting on the false assumption that gay men were more likely to have unsafe sex.
The Human Rights Commission agreed that, on the face of it, the policy appeared to be discriminatory.
Wellington Hospital infectious diseases specialist Tim Blackmore said the policy was similar to the Blood Service's blanket exclusion of those who spent more than six months in Britain between 1980 and 1996, because of the risk of fatal brain condition variant Creutzfeldt-Jakob disease.
"I don't think it is homophobic. It is just risk management."
Gay men were a higher risk group and it was possible for someone incubating the disease to have a negative HIV test, but for the semen to then infect the mother and baby.
However, with the changing pattern of HIV infection, it may be time to review the policy, he said. A homosexual man in a constant relationship with a single partner was probably a safer bet than a highly sexed heterosexual man.