The High Court has found a man who donated his sperm to a lesbian friend to have a child is the father, due to his involvement in the girl's life.
Lawyers for the donor, named as Robert Masson - a pseudonym used by the court - argued Commonwealth law should apply, rather than the state law, which says a sperm donor is not a parent.
Under commonwealth law Mr Masson is considered a parent, as he is the biological father and is involved in the child's life.
The High Court agreed, saying in a summary of its judgment on Wednesday: "The majority held that no reason had been shown to doubt the primary judge's conclusion that the appellant was a parent of the child."
The court said Mr Masson had donated his genetic material in a private, personal insemination to his friend of some 25 years in 2006.
But he had taken the matter to the Family Court after his friend and recipient of the insemination, named under the pseudonym Susan Parsons, met her partner Margaret and they tried to move to New Zealand.
Mr Masson's lawyers had argued that as he had had considerable involvement in the child's upbringing, including volunteering at the school canteen, he was considered the father, not simply a donor.
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In its decision, the court affirmed a previous decision of a Family Court judge that there was no reason to doubt the original decision that the man was the child's parent.
Mr Masson had been involved in the child's life and her younger sister's care, and both children called him "Daddy", court documents show.
He was also named as the child's father on her birth certificate.
Commonwealth Solicitor-General Stephen Donaghue had argued the state laws in the matter were irrelevant and over-ridden by federal statute, though the Parsons had argued Mr Masson was simply a sperm donor and not a parent.