A stark warning young children should never be left unsupervised in child restraints -- no matter how long

A nine month old died after becoming caught in the harness of her car seat while drinking a bottle of milk.

Coroner Janet Anderson says the car seat wasn't strapped into the vehicle, and while the chest harness was secure, the crotch strap was left unbuckled, and the straps left loose.

Plunket Clinical Advisor Karen Magrath says these restraints can be extremely dangerous.

She urges parents to continue seeking information on age-related car safety for children.