Ancestry websites should be 'forbidden' because they risk sperm donors being contacted by their children against their will, an expert has claimed.

Men in the UK were allowed to donate sperm anonymously until 2005 in the UK and could now have their identities discovered by people researching their family trees.

This, according to Professor Guido Pennings, a bioethicist at Ghent University in Belgium, constitutes a violation of the father's privacy.

Although some donors are willing to be contacted by any children born using their sperm, those who weren't may not be able to avoid being found out online.

Sperm donors could be found out against their will by children using ancestry websites, which constitutes a violation of their privacy, according to one expert (stock image)

'Users violate a person's privacy when they identify and/or contact a person who is not registered on the database,' Professor Pennings said.

'This is especially wrong for [sperm] donors since they have been promised anonymity and are betrayed by the searches.

'People who use ancestry databases to find a donor show disrespect and lack of gratitude.'

He made the comments in the scientific journal Human Reproduction.

Men were allowed to donate sperm anonymously until 2005 in the UK, suggesting there are donor-born adults now who can't find out who their fathers are.

But these men could one day be identified through the genealogy websites even if they haven't added their own information or genetic details, experts said.

As the use of advanced DNA testing becomes more popular, people stand a greater chance of finding close biological relatives online.

HOW COULD A SPERM DONOR FATHER BE FOUND ONLINE? Professor Guido Pennings, a bioethics researcher at Ghent University in Belgium, said it was a 'violation of sperm donors' privacy' to allow them to be found unwillingly by their offspring online. Men who donated sperm in the UK before 2005 were able to choose to hide their identity from any children born from their DNA, although this is no longer allowed. If a child born from anonymous donor sperm decided to take a DNA test and trace their ancestry, they could find out who their biological father was if he, or other relatives of his, were already on the website. Even if the father hadn't been tested or signed up to the website himself, other members of his family who do know him may have filled in his space on a family tree. And if the donor child was able to connect with biological siblings online this could link them back to the sperm donor without his knowledge. Advertisement

But even if a donor has never used one of the sites, other members of their family may have filled in his space on a family tree, for example.

If another user matches with a child, sibling or other relative of the donor they may be able to track down and contact their biological father, Professor Pennings said.

Donors who had been promised anonymity by a clinic could therefore be discovered without anyone's knowledge – and neither would be able to stop it happening.

Men in the UK are no longer allowed to donate sperm anonymously and must allow any children conceived with their DNA to find out who they are.

Professor Pennings admitted his concerns only applied to a very small minority of people, but still went as far as to say access to the family history sites should be forbidden, The Times reported.

Professor Pennings wrote: 'Control is very difficult if not impossible if the online genetic testing companies are located in a jurisdiction that does not forbid these activities.'

And he added: 'Limiting access may in fact be the easiest way to proceed.'

Websites including Ancestry and 23AndMe contain databases and anyone can pay to take DNA tests and find out about their family history.

People who didn't know they were conceived using donated sperm could also be contacted by biological siblings, Professor Pennings warned.

This could cause distress and upset in a wider network of people who may never have known the others existed if it weren't for the websites.

Men who donated sperm in the past and now live with new relationships and other children could be disturbed by offspring they didn't know about contacting them.

However, Professor Pennings comment were not echoed by all and were described by ' grossly offensive' by one critic.

A genealogist at University College London, Debbie Kennett, told The Times the research 'fails to recognise the rights of donor-conceived individuals'.