Experts are calling for better recording and sharing of information to help tackle child abduction in the UK.
A national child abduction "hub" should be created to give a clearer picture of the problem and provide data and support to improve how agencies deal with abductions, according to Ceop, the Child Exploitation and Online Protection Centre, and the charity Parents and Abducted Children Together (PACT).
A report from the two organisations found that almost half of child abduction cases reported in the UK between 2011-12 were committed by strangers. The report was based on police data that included 592 cases involving 675 victims.
In 42% of police reports - 247 out of 592 cases - the abductor or would-be abductor was not known to the child. A further 17% were abducted or victims of attempted abductions by a parent, 2% by another family member and 35% by someone known but not related to the child. Another 4% were by unknown offenders.
The report, "Taken - a study of child abductions in the UK", warns that at present the true extent of child abductions is "impossible" to calculate with the necessary accuracy because of inconsistencies in the recording of offences.
It reveals that details of different types of child abductions and held by police forces, government, legal bodies and voluntary agencies, but says that this information is not always published or made routinely available.
The report, which comes ahead of International Missing Children's Day on Saturday, sets out 14 recommendations, including agreeing a UK-wide definition of child abduction and improving how police record and respond to incidents. It also calls for a revamp of current "stranger-danger" warnings for children, and suggests there should be better learning from why so many attempted stranger abductions fail.
Geoff Newiss, PACT's director of research and author of the report, said: "This new report exposes the reality of child abduction in the UK today. Whilst children are abducted by parents and people known to them, a large proportion of incidents still involve strangers, often trying to lure a child into a car, and sometimes succeeding in doing so."
Lady Catherine Meyer, founder and chief executive of PACT, said: "Many will find its revelations shocking. More importantly, by showing the extent of this hidden scandal, PACT's report provides a vital platform for future action. The next stage of our work will be entirely focused on the practical steps necessary to protect our children from the would-be abductor."
In 2011, Ceop took over the national strategic lead on missing children and now collaborates with partners to better understand and address the issue. Chief executive of Ceop, Peter Davies, said the report shows the immense harm that child abduction can do. He said: "Together with our partners, we must constantly redouble our efforts to reduce the risk to children. International Missing Children's Day is a good opportunity for us to reflect on this important and complex issue."