The family of school principal Hawea Vercoe says his killer should serve at least 20 years in jail, not the two years and 10 months he got for Mr Vercoe's manslaughter.
The family is now petitioning to have the sentence passed on Isaiah Tai, 21, extended to 20 years.
Tai pleaded guilty in the High Court at Rotorua in April and was sentenced earlier this month.
Mr Vercoe's family said at the time of Tai's sentence that two years and 10 months was not enough.
Mr Vercoe died after Tai punched in the back of the head, then kicked in the head as he lay unconscious outside a Whakatane bar in November.
He died later in hospital.
His aunt Rihi Vercoe said the collection of signatures for a petition would be part of a nationwide appeal for a mandatory sentence of 20 years for taking a person's life, the New Zealand Herald reported today..
She said the sentence cheapened the life of an aspiring Maori leader and father of six.
The family would send the petition to the Crown Law Office and the Attorney-General, encouraging an appeal.
NZPA