The Supreme Court has denied an appeal over the murder conviction of a man who beat a two year old to death.

The chilling confession of Rikki Ngati-Check shocked a Whanganui High Court jury when the case was heard five years ago.

Since then he's been trying to get his conviction overturned with his defence team saying he didn't have murderous intent.

Ngatai-Check had lost his temper with the baby and kicked him with force in the stomach twice.

His lawyers argued that testimony from a paediatric surgeon that the fatal kick had been delivered "with venom" was highly prejudicial.

But the Supreme Court has said the judge at the time gave strong direction to disregard it.