One in 25 fathers could unknowingly be raising another man's child, according to new research.
New genetic techniques have opened a "Pandora's box" of hidden aspects of sexual behaviour, a team from Liverpool John Moores University said.
They said that the implications of so-called paternal discrepancy are huge, and more research is needed to determine how widespread the problem is.
Increased use of DNA profiling and genetic testing has been seen in recent years and is relied on in areas such as organ donation and criminal investigations.
The researchers, led by Professor Mark Bellis, examined a wide range of international studies looking at estimates of paternal discrepancy between 1950 and 2004.
They found that rates of cases where a father was not the biological father of his child ranged from 1% in some studies to as much as 30%.
Experts have generally agreed that the rate is below 10%, with a 4% rate meaning that about one in 25 families could be affected, the study said.
But the researchers, writing in the Journal of Epidemiology and Community Health, said that increased use of genetic testing for diagnosis, treatment and identification was likely to boost rates of paternal discrepancy.
This made the need to understand the true prevalence of the problem even more pressing.
The researchers said: "For any father, identifying that the child they are raising as their biological progeny is actually sired by another man can have substantial health consequences.
"Such knowledge can also destroy families, affecting the health of the child and mother as well as that of any man who is ultimately identified as the biological parent."