The Sensible Sentencing Trust will today present its 'Justice for Moko' petition to Parliament.
It follows nationwide marches protesting the manslaughter convictions given to the killers of three-year-old Moko Rangitoheriri.
Tania Shailer and David Haerewa abused and neglected the three-year-old for two months before his death in August last year. They were supposed to be looking after him while their mother Nicola Dally-Paki was at Starship Hospital caring for one of her other children.
It was described by the sentencing judge as one of the most serious cases of manslaughter she had ever seen, and they were jailed for 17 years.
Sensible Sentencing Trust spokesman Scott Guthrie says they should have been tried for murder.
"It's in the interests of Crown Law to reduce that down to manslaughter to get a plea of guilty so it doesn't have to go through the court system and the case is over and done with, out of the way, and they get paid."
The group today will hand over a petition today, which has been signed online by more than 6600 people. It will be received by MPs from NZ First, Labour and the Maori Party.
"Now it's up to the politicians to take notice," says Mr Guthrie.
The petition has two demands:
The group will meet at Midland Park on Lambton Quay at noon, before marching to Parliament and handing over the petition at 1pm.
Mr Guthrie hopes the petition will be put before a select committee and lead to a change in legislation.