New Zealand's child abuse record is brutally laid bare in one of the most comprehensive releases of Government data on the nation's bruised and broken children.

There are 22,000 substantiated child abuse cases each year, resulting in around 1000 prosecutions and 128 recorded hospital admissions.

One expert says child abuse rates are not falling and it's time we developed reliable measures to quantify the horrific harm suffered by children.

The child abuse rates, prosecutions and hospital admission figures – released under the Official Information Act – highlight stark differences in reporting.

A number of hospitals are failing to record suspected rates of child abuse, while other hospitals have been accused of pointing the finger at innocent parents.

In Northland, where more than 1300 child abuse cases arise each year, the hospital does record suspected child abuse and refers questions on to Child Youth and Family (CYF).

Chief executive Nick Chamberlain said the responsibility of determining child abuse rests with CYF and Police.

In contrast, Auckland's Starship Hospital and Waikato District Health Board were able to provide detailed data on suspected and definite child abuse assaults and deaths.

Blows to the head and broken bones were the most common forms of assault on a child, but doctors also treated open wounds, eye injuries, severe bruising and fractured vertebrae.

The alarm is also being raised on less visible injuries: neglect, sexual abuse and threats to an unborn child.

Dr Eleanor Carmichael, a paediatrician at Waikato Hospital, said very rarely will doctors know immediately if a child has suffered abuse.

Children with head injuries may be having fits and be unwell, but show no bruising or marks.

It is only after investigating that it can become apparent why a child suffered a head injury.

There are also the finer lines of neglect, where a lack of nutrition, passive smoke inhalation or mouldy homes contribute to regular hospital visits.

"A lot of our work in health and welfare is the kids who live in poverty and parents who, for whatever reason, can't provide them with a good or optimal home environment," Carmichael said.

Doctors do not accuse parents, she said, but rather refer concerns on to the hospital social worker and CYF.

"What we do is we let the care and protection service know there is a very unhealthy situation that doesn't make medical sense.

"The information we share is an important piece in a jigsaw puzzle they are building.

"It's really important that we hand over the pieces."

Last month, the Sunday Star-Times revealed a father had been wrongly accused of shaking or throwing his four-month-old daughter so hard she suffered brain injuries.

The father is now battling to convince Child, Youth and Family to let him have access to his two children, including the girl, who has fully recovered. CYF figures show a sharp increase in child abuse, from 19,596 to 22,087 in the past three years.

There were 1126 cases of substantiated sexual abuse in 2009, jumping to 3225 in 2011. About half of all abuse is classified as emotional.

Otago University child abuse researcher Dr Pauline Gulliver said while the figures were a cause for concern, they must be treated warily, as hospital admission and CYF data can change with social and policy trends.

"We have some work to do to develop reliable measures of child maltreatment rates before we can confidently say what is happening with child maltreatment in our community."

Child, Youth and Family chief social worker Nova Salomen said they determined whether abuse had occurred after careful consideration of the circumstances, including the level of harm caused to the child.

A finding of abuse does not necessarily lead to criminal charges for a number of reasons.

Often, if the victim is a young child who is yet to start talking, it can be difficult to establish what happened, he said.

It may also be difficult to identify the offender, or the abuser is a teenager or young person who is handled in the Youth Court.

Police national crime manager Detective Superintendent Rod Drew said CYF's 22,000 cases cover a broad range of welfare issues.

Police focus primarily on victims and prosecutions.

"Police get the top end of the scale."

In 2010, police received about 4000 reported cases of abuse, and, of those, 1700 resulted in prosecutions.

According to the Ministry of Justice, those prosecutions resulted in 963 convictions for violent offences against children.

Police weigh up whether there is sufficient evidence and if it's in the public interest to prosecute.

"It is a very robust process."

Police were striving all the time to do better investigations and the partnership between police and CYF was strengthening, Drew said.

The experts agree there is more being done than a decade ago.

Carmichael said anti-violence campaigns have helped, including pamphlets, television advertisements and educating parents.

The Government is also considering strengthening measures to remove babies from parents who seriously abused or neglected their children.

- © Fairfax NZ News