The Sensible Sentencing Trust is calling for a royal commission of inquiry into how the horrific death of a Taupo three-year-old was reduced to the "shallow charge of manslaughter".
The manslaughter deal in the case of Moko Rangitoheriri "smacks of collusion of the highest degree", the trust says.
Moko who suffered terrible fatal injuries at the hands of his carers last year. David William Haerewa, 43, and 26-year-old Tania Shailer were initially charged with murder but pleaded guilty to the lesser charge on Monday.
They had been looking after Moko while his mother attended to another child in Auckland's Starship Hospital.
"This case is Lilybing, Nia Glassie and the Kahui twins all rolled into one," said trust child abuse spokesman Scott Guthrie.
"The assault was premeditated and prolonged fitting all the criteria for murder. The fact the crown have accepted a guilty plea of manslaughter smacks of collusion of the highest degree and is symbolic of New Zealand's horrific level of child abuse."
Murder was defined as when the offender had been so reckless and means to cause such bodily injury to one person even though he or she does not mean to hurt the person killed, he said.
The trust wants Governor General Sir Jerry Mateparae to initiate a Royal Commission of Inquiry into Moko's death.
The inquiry should "find out how a child's life can be worth so little and how the most serious crime of murder can be reduced to such a shallow charge of manslaughter", Mr Guthrie said.