Dutch fertility clinics have deliberately flouted the rules around sperm donorship for over 20 years, resulting in at least 85 mass donors, the organisation for gynaecologists NVOG has confirmed to current affairs programme Nieuwsuur.

Until recently, Dutch fertility clinics had a limit of 25 children per donor.  That has now been brought back to 12.

But until then, donors were able to register at several clinics at the same time, and some clinics deliberately used donated sperm more than 25 times without the knowledge of the donor or the mothers involved. Clinics also exchanged sperm without the proper paperwork and knowledge of the donor, the NVOG said.

The organisation is calling on mothers, donors and donor children to contact their fertility clinics for more information. “The number of mass donors should have been zero,” gynaecologist Marieke Schoonenberg told the programme. “We want to apologise on behalf of the profession, we have failed people,” she sai

The new law on artificial insemination, which came into effect on April 1, limits the number of children fathered by a single donor to 12 and donors and mothers are registered in a national register. The register will go back to 2004, when anonymous donation was banned.

The number of children per mass donor varies from 26 to 40, but includes several with over 50 to 75. At least 10 fertility doctors illegally used their own sperm, including Jan Karbaat, who fathered 81 children.

Registration at the Leids Universitair Medisch Centrum (LUMC) sperm bank was a shambles, with donor data going missing and some donors fathering over 25 children in the same area, increasing the risk of incest. the hospital admitted following an internal investigation.

Another high-profile case featured Jonathan Jacob Meijer, who fathered 550 children worldwide.

Ties van der Meer of Stichting Donorkind, which helps children track their donor fathers in commercial data banks, said the numbers mean there are “at least 3,000 children involved, each with more than 25 half-siblings,” he said.

Van der Meer said the scandal has eroded trust in the medical system and the governments which have allowed it to happen. The fact that donor children will turn out to have more half-siblings will lead to extra stress for parents and children, he said. “The children will never be able to date without having to do a DNA test to see if they are related,” he said.

The health ministry has said in a reaction it will address the findings in a briefing to MPs later this week.