A couple left "devastated" when they were caught in a legal bind after their fertility treatment documents were lost have won a landmark High Court ruling.
The pair became parents to twins born after using a sperm donor in Nottingham but consent forms went missing.
It meant they could not register the father on the birth certificates.
But a top judge said the man should be recorded as the father and registrars' guidelines should be revised to stop the situation happening again.
After the twins were born, officials twice refused to record the man as the father because forms which showed the couple had consented to the donor treatment were missing.
The court in London heard they felt "no choice" but to register the children's births with the boxes identifying their father left blank.
Sir James Munby, the country's top family judge, was told by the man: "I cannot express how I feel about not being recorded on my children's birth certificates as their father.
"The thought of not being their father has caused me a huge amount of worry".
In his ruling, Sir James not only ordered the man to be registered as the father but also for new birth certificates to be issued.
He did so because had the original certificates been amended the role of the donor would have been obvious to anyone who saw them and the parents had not intended to inform their children "they were conceived using donated sperm".
He said: "Put starkly, the state by its actions has denied these parents the right to decide for themselves, within the privacy of the family, what in their view, as devoted parents, is in the best interests of their children.
"Though without any malign intent, the state has intruded into very private and personal matters which, as I have said, are none of its business".
While he accepted registrars had followed the official handbook, Sir James said it would have to be re-written in the light of his decision.