There are no official figures on child abuse, but the National Crime Agency has estimated that there were 2.6 million recorded cases in England and Wales in 2011.
That compares with 5.3 million in 2007.
In a report released this month, the agency said it had seen a significant increase in the number of children being subjected to physical or sexual abuse.
The agency said the number was more than triple the rate of other countries.
The increase has been partly caused by more people reporting incidents, the report said.
The National Crime Authority says there were 4,093 children, aged from four to 16, reported to police in 2011-12, compared with 3,715 in 2006-07.
In some cases, it has estimated, there were more than 50 children under the age of five under the care of a family member.
The number of cases that were not reported to the police rose to nearly 3,000 from 1,900 the previous year.
While there were fewer children under five under care, the National Child Abuse Prevention Strategy found that a number of factors were responsible for the decline.
Child protection workers have been encouraged to report suspected child abuse to police and to take urgent steps to protect the vulnerable.
Many child protection services were unable to meet demand, the government said.
The Children’s Commissioner said the agency had seen an increase in referrals and referrals to other services.
A spokesman for the police service said that the increase in reports had to do with more victims coming forward, not a decline in reporting.
An estimated 25,000 to 30,000 people were under investigation in England last year, and some police forces have received referrals from the National Centre for Missing and Exploited Children, the spokesman said.