Social networking websites such as Facebook can pose a serious risk to adopted children who can be easily tracked down by birth relatives they may not be ready to meet, a charity has warned.

While there are no precise figures on the number of children who have been contacted in this way, David Holmes, chief executive of the British Association for Adoption & Fostering (BAAF), says the phenomenon is a growing concern.

"It's not just Facebook, it's the whole phenomenon of social networking and social media. There is a very positive side to it, because it's a way of keeping in contact with lots of people very easily... But equally, by having lots of friends and posting identifying information online, that information could be misused in the wrong hands," he told The Independent.

"For children who – for whatever reason – may need to keep some privacy and to be quite careful about online safety, this is a real issue."

Under the Adoption and Children Act 2002, a birth relative would normally have to wait until the adopted child turns 18 to initiate contact. This would usually be done via a third party – such as the adoption agency or a local authority – with procedures in place designed to protect the confidentiality of both sides.

As some children do not know why they were placed in care, BAAF says, they may not understand the risky situation they may be putting themselves by disclosing personal details online or exchanging messages with a birth parent.

In cases where a child is not necessarily in physical danger, the charity's primary concern is theemotional impact of such a sudden and unexpected reunion.

"The problem is that this form of contact is potentially so fast and so immediate that all of the careful planning that would normally go into contact arrangements goes straight out the window," Mr Holmes said.

"If you were going to make contact with a birth relative, you might do it through an exchange of letters, or even through an exchange of photographs. Through this [social networking] route you can cut through this completely and find that within 10 minutes or an hour you're having an online conversation."

BAAF's advice for adoptive and foster parents includes: refraining from "tagging" their children in photos on Facebook; helping them adjust their privacy settings so that their profile cannot be seen publicly; ensuring they do not share their date of birth, address or school details; and making sure they know how to block other users if they are contacted and the contact is unwelcome.

According to Holmes, it is not just children who can become distressed due to unwanted contact from their birth relatives; adults approached by a child they gave up for adoption can find the situation equally upsetting. "There are lots of difficult issues wrapped up with adoption; there are lots of personal and emotional issues, and suddenly this form of networking can cut through all of those," he said. "It's an issue for birth families too."

There are dozens of Facebook groups dedicated to reuniting families separated by adoption. Most users post details of their or their child's birth in the hope that someone may recognise them. A few have written comments about successful reunions. "My first daughter found my second daughter on one of these sites, and now she has found me too," wrote one user from Northampton.

drive from www.independent.co.uk