A man charged with fatally assaulting a six-month-old baby at Raumati Beach has had his charge upgraded to murder.

Gracie May McSorley died in July.

At the time Michael Kereopa was charged with assault - and claimed the baby's injuries came through an accidental fall.

Michael Keroapa was largely unemotional when he appeared in court this morning, standing in the dock calmly and solemnly.

Police say Gracie's mother was in a brief relationship with Kereopa at the time the baby died.

They say the injuries the six-month-old suffered before her death were similar to what would be sustained in a high-speed car crash.