The ContactPoint system, built by Capgemini, was intended to ensure none of the 11m under-18s in England could slip through the child protection net.
The system was planned after the torture and murder of eight year-old Victoria Climbie in 2000, by her aunt.
But the London Evening Standard reports government guidance reveals the ContactPoint database can now be accessed "for the prevention or detection of crime" and "the prosecution of offenders".
ContactPoint, when it goes live later this year, will include children's names, their ages and addresses, plus details of their parents, schools, medical records and social workers.
The government says it will connect the different services dealing with children. The Government says this will allow police, council staff, head teachers, doctors and care and probation workers to more easily see if a child is at risk.
Officials now admit the records can now be checked by police for evidence of criminality.
The Liberal Democrats described police access to the database as evidence of a "police state".
The government says ContactPoint will provide a quick way for practitioners across education, health, social care and youth offending to find out who else is working with the same child.
Privacy groups have raised concerns about the children's database after several public data leaks from government departments. The government said the database will contain only basic information and no case details.