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Children's Commissioner Cindy Kiro backs calls for harsher punishments for people who harm children.

However, she said society needed to take action to prevent people abusing children before the courts system dealt with the aftermath of deaths like that of Rotorua 3-year-old Nia Glassie.

Nia died on Friday, and five people face criminal charges stemming from police investigations into her death.

Yesterday National leader John Key said he had been sickened by the manner of Nia's death, and promised severe punishment for child abusers under any government he led.

The Sensible Sentencing Trust also reacted angrily, calling for a mandatory 20-year non-parole period for anyone found guilty of child murder.

Dr Kiro said sentences for attacks on children clearly needed to be looked at, and there was a need to make some sentences more severe.

"However, it is the end of the road, and it worries me that we get so fixated about looking at the end of the road ... It's how do we stop people from actually being so abusive?" she said.

"I think we have a pretty good idea what needs to be done. The statutory agencies want to get on and do it, the community agencies want to get on and do it, but it is going to take political will, public appetite and finances."

The Herald On Sunday reported that Lisa Kuka, Nia's mother, previously had a child seized after the child suffered non-accidental head injuries. Child, Youth and Family did not monitor her subsequent children.

CYF refused to comment yesterday.

"Right now five individuals have been charged with offences relating to the horrific abuse inflicted on Nia," chief executive Peter Hughes said.

"What is most important now for everyone concerned is that those responsible are held accountable. CYF is supporting police in their investigations, and we will be making no further comment until their investigation and court processes are complete."

Since the Glassie case hit the headlines, CYF had noted a sizeable jump in the number of phonecalls about possible cases of child abuse.

Dr Kiro said she was "keeping her finger on the pulse" of the Glassie case, but would not begin any investigation of her own until the police inquiry and court action were completed.

However, the case did highlight the need for a system which clearly indicated when a child was at risk of being abused, so agencies could step up their involvement with those families.

"It's not the case that everybody who has had a child removed by Child, Youth and Family is a bad parent and cannot parent again. It is the case that they need to be monitored more carefully," Dr Kiro said.

"There should be a red-flag system. Yes, I do think it warrants more pro-active monitoring where high-risk factors exist, one of which is a child has been previously removed because of a suspected non-accidental injury."

Many of the police investigating Nia's death had the weekend off. Detective Senior Sergeant Mark Loper, the inquiry head, had said investigations would scale back during Nia's tangi.