A police officer has described injuries that hospitalised a 4-year-old boy as some of the most severe he's seen on a child in 30 years on the force.

Photo: RNZ Insight / Anneke Smith

The child received the injuries in Ramsey Crescent, Flaxmere, in the Hawke's Bay on 29 January.

He remains in a serious condition in a ward in Starship Hospital and is likely to be severely disabled and brain damaged if he survives, according to police.

Detective Inspector Mike Foster told RNZ: "What I can tell you is these injuries were not accidental. These injuries were not self inflicted. This child has undergone a beating or a number of beatings by somebody and as I said, the injuries sustained to this poor child are horrific."

He would not specify the injuries the boy received but did say one was a severe head injury and others were "extensive" across his body.

"It's certainly up there with the worst I've seen."

He said it wasn't yet clear how the boy had received the injuries.

Some may not have been received at the same time, he said.

A number of people are being spoken to in relation to the incident but police are seeking more information which may help their investigations.

Foster said: "We would urge people to do the right thing by this child and help us work out exactly what's happened. Please let us know anything that may help, no matter how small."

Police were speaking to people at the address on Ramsey Cresent as well as extended whanau. There were a number of family members with him throughout the day he was injured, Foster said.

"The parents were at the address, there were times when they weren't we're still trying to ... understand what exactly happened."

Foster said the family were "not in a good space" but police were working with them to find out what had happened.