Around one in 25 dads could unknowingly be raising another man's child

The implications are huge, say the authors, with the increasing reliance of judicial and health systems on DNA profiling and genetic testing, such as organ donation and criminal identification.

The authors base their findings on wide ranging and international published scientific research and conference abstracts, covering the period between 1950 and 2004.

Their findings show that rates of "paternal discrepancy" - where a father is not the biological father of his child - range from less than 1% to as much as 30%.

It is generally thought that rates are below 10%: a rate of 4% means that around one in 25 families could be affected.

However, increasing use of genetic testing for diagnosis, treatment, and identification is likely to boost the rates of paternal discrepancy, say the authors, making the need to understand the true prevalence even more pressing.

They point to other supportive evidence, including soaring rates of paternity testing in North America and Europe. In the US, rates more than doubled to 310,490 between 1991 and 2001.

In the UK, around a third of pregnancies are unplanned, and around one in five women in long term relationships has had an affair, with similar figures reported from other developed countries.

And at present there are few support services to help those affected and little guidance on the disclosure of paternal discrepancy for those working in healthcare or the criminal justice systems.

"In a society where services and life decisions are increasingly influenced by genetics, our approach to [paternal discrepancy] cannot be simply to ignore this difficult issue," conclude the authors.