Jonathan Pearce, chief executive of Adoption UK, said it was having to deal with the consequences of this “intrusive and unplanned communication”, and warned that it was becoming more difficult to guarantee confidentiality to adoptive parents and their children. At the moment, official contact in adoption is most often made through the “letterbox” process. The adoptive parents send the birth family a letter and photos every year via a social worker or adoption agency intermediary. If the birth parent wants to respond, they also have to go through this route.

However, Facebook and other social networking sites have changed all this. Any scrap of information – a name, location or date of birth – can help biological parents track down their children. But the agencies warn that the existing rules protect often extremely vulnerable children. Where once adoption tended to involve a young, single woman giving up her unplanned baby, now two-thirds of adopted children have been removed because their parents abused or neglected them. In many cases, the birth parents dispute the removal, blaming social services.

One message sent to a child given up some years ago for adoption read: “Hello, I’m your birth father. I have been searching for you ever since you were stolen by social services. You look beautiful. I love you so much.” Another read: “Darling son, I am so happy because I have found you here. I have been looking for ages. Please write back because you’ve been told lies about me.” Many local authorities are now advising adoptive parents not to include photographs in their annual letters, in case these are posted online in an attempt to trace the child.

With two news videos.