Child safety advocates say a record jail term given to a child murderer demonstrates a zero tolerance of child abuse.
Joel Loffley was sentenced to serve at least 19 years in prison for killing his two-year-old stepson James Lawrence, known as JJ, in November 2011.
The minimum non-parole period given at the High Court in Auckland on Thursday is believed to be the longest given to a child murderer in New Zealand.
Child Youth and Family had been alerted to JJ's situation and a social worker visited the home several times in the four weeks before he died, but could not locate him or his mother.
The agency says it now knows those in the house were lying about people's identities, the relationships between them and who was living there.
Executive director of Maori child advocacy organisation Ririki, Anton Blank, said the long sentence sends a clear message that horrific abuse is not acceptable.
But he said it is clear other adults living in the house knew what was happening, and they should also take responsibility for not stepping in to save the toddler.
Anthea Simcock, chief executive of Child Matters, said the sentence sends a message that this type of treatment of vulnerable children will not be tolerated. Child protection group Jigsaw said the courts were responding to the horrendous nature of the crime.