One in 10 children may be suffering from abuse in the developed world, according to a series of studies on child abuse published in the Lancet medical journal.
The authors from British and American universities warn that child abuse is much more widespread than indicated by official child protection statistics.
Professor Ruth Gilbert of University College London said that, based on a number of academic studies in which adults were asked about whether they had been abused, and parents about their own disciplinary methods, it was estimated that a tenth of children had experienced abuse.
The definition of abuse included punching, hitting, beating, burning, rape, exposure to pornography as well as neglect and emotional abuse such as making a child feel worthless or unwanted.
Maltreated children are at increased risk of perpetrating crime and violence as adults, thereby perpetuating the cycle of violence at considerable cost to themselves, their families and wider society," Professor Gilbert wrote.
Her study estimates that at least 15% of girls and 5% of boys have been exposed to sexual abuse of some kind by the age of 18, and that 5-10% of girls and 1-5% of boys are exposed to penetrative sexual abuse.
The authors are concerned that too many instances of child abuse go unreported as people fear being accused of breaking up families.
Professor Gilbert said: "Scarce reporting to child-protection agencies is a cause for concern, and we need to find out whether maltreatment is being recognised and dealt with in other ways."
The study calls for better cooperation among doctors, schools and child service agencies and increasing the use of telephone helplines and confidential counselling.
The authors conclude: "Child maltreatment is common, and for many it is a chronic condition, with repeated and ongoing maltreatment merging into adverse outcomes throughout childhood and into adulthood... More attention needs to be given to neglected children. There is mounting evidence that the consequences of childhood neglect can be as damaging - or perhaps even more damaging - to a child than physical or sexual abuse."