Hundreds of thousands of children abused in their own homes are slipping through the net as local authorities are unable to protect them, one of the largest children's charities in the UK has warned.

More than half a million children are abused or neglected at home each year - but just one in nine are protected by local authorities, the NSPCC said.

Services to protect children are improving but the charity warns they will only ever reach a fraction of the children who are abused. The scale of the problem is a key finding in the UK's first national child abuse tracker How Safe Are Our Children launched by the NSPCC.

Lisa Harker, NSPCC head of strategy and one author of the report, said: "As a nation we spend more than £6 billion every year on services for children and families. We need to know if our efforts to prevent abuse and protect children are working.

"Child protection services are working in overdrive and our report shows the UK is making progress in some areas. But the hidden extent of child abuse and neglect revealed in this report is a national scandal.

"Since Baby Peter, social workers and other professionals are working harder and harder to reduce the harm caused by abuse and neglect. They are taking more referrals, making more assessments, providing more services and putting more children in care. When we discover abuse, we must do everything we can to protect children from further harm and help them recover.

"But it's vital to prevent abuse from happening to so many children in the first place. We need to shift policy across the UK towards early intervention - and set a new course that can stop cruelty blighting so many children's lives."

Its new report reveals that for every child subject to a protection plan, or on child protection registers, another eight have suffered recent maltreatment. The NSPCC estimates that 520,000 children were maltreated by a parent or guardian in the UK in 2011 but only 58,000 became the subject of child protection plans in that year.

Minister for children, Edward Timpson, told the NSPCC's conference in central London that the fight against child cruelty "tests society as no other issue".

"We need to do more to intervene earlier and more effectively, especially in a technological landscape which is rapidly changing," he said. "There is nothing more important than protecting children from harm. Where children are suffering abuse or neglect they should be taken into care more quickly. By refocusing the system on children's needs through our reforms, we will help ensure each child gets the right support at the right time."