A coroner has recommended changes to mental health laws after a woman escaped a Waikato mental facility to bludgeon her neighbour to death.

In January 2010 Christine Morris scaled a fence at the Henry Bennett Centre to murder Diane White with a hammer in her Frankton home.

Despite announcing she was going to kill Mrs White, nurses couldn't stop Morris leaving as she was a voluntary patient.

Coroner JP Ryan says the legislation should be changed to give nurses the power to immediately detain voluntary inpatients in the need arises.

He's written to the chief executive of the Ministry of Health.