A Dutch judge has ordered a "mass sperm donor" who's already fathered at least 550 children to stop donating.

The man donated sperm in the Netherlands and abroad, including to Danish sperm bank Cryos, but also offered his sperm up via online platforms.

He donated to at least 11 Dutch fertility clinics, which imposed a maximum of 25 children in 12 families per donor, while making false promises that he hadn't offered his sperm elsewhere and wouldn't do so in the future.

In 2017, it was discovered that he'd already fathered 102 children via those clinics.

The judge ruled that the man "deliberately lied to get parents to pick him as a donor," knowing full well that they wouldn't have chosen him if they'd known how many children he'd already helped conceive.

The man claimed he was acting in the interests of prospective parents, who he wanted to help.

One mother and Stichting Donorkind, an organization that represented several of the man's donor children and their parents, had turned to the court in The Hague to demand that he be stopped from donating, and that the sperm he'd already donated no longer be used.

The group argued that by exceeding the 25-child or 12-family limit — by far — the man risked harming his donor children's mental well-being, while increasing the risk of incest.

"All these parents are now faced with the fact that their children are part of a huge kinship network, with hundreds of half-brothers and sisters," the court said.

The judge banned the man from donating his semen, or advertising as a donor, and ordered him to declare within seven days whether he had donated to more clinics.