An organisation which helps donor children track down their biological fathers has identified at least 10 doctors who have illegally used their own sperm, news website Nu.nl said on Monday.

In the past five years, Stichting Donorkind, which helps children track their donor fathers in commercial data banks, has identified 10 gynaecologists among 150 to 200 donors.

Unlike Jan Karbaat , who fathered 81 children at the last count, and other high-profile cases such as Jan Wildschut  and Jos Beek , not all cases were brought to the attention of the media,  spokeswoman Ester de Lau told NU.nl.

Publicity around the subject is not always welcome and that is why the organisation and the children are keeping the information to themselves, De Lau said.

‘Donor children do no want everyone to comment on their donor father. They are the ones who have to figure out their relationship with him, if they want to contact him or other relatives,’ she said. ‘To be ‘one of the doctors’’ is an extra hurdle.’

However, every time there is news of yet another fertility doctor using his own sperm, donor children are prompted to contact the organisation. ‘It also helps parents to discuss the subject with their children,’ De Lau said.

Dutch law limits the number of children that can be conceived from one sperm donor to 25. Since 2004 children have had the right to know the identity of their biological parents once they reach the age of 16.