The other two children - aged three and four - were unrestrained in the centre of the back seat," he said.
The woman was breath tested and blew a 856 micrograms of alcohol per litre.
The legal limit for drivers aged 20 and over is 250 mcg.
"That result is well over treble the adult limit and, had our officers not intervened when they did, there's no telling how that journey might have ended for her, her passengers or others using the road," said Mr King.
"It beggars belief that parents could choose to put such precious cargo as their own children in such vulnerable situations."
Mr King said police spent "considerable time" organising appropriate transport for the children to be safely delivered to their respective homes last night and arrested one intoxicated passenger for obstruction during the process.
Police have referred the incident to Child Youth and Family. The woman has been charged with drink driving and will appear in the Auckland District Court.
Mr King said it was possible further charges will be laid.
"But for the actions of police, the families involved could have become further summer tragedies," he said.
"Adults need to take responsibility for their decisions and ensure that they don't put children, who have no input into such decisions, unnecessarily in harm's way."
Under New Zealand law, all children under 7 years of age must use an approved child restraint appropriate for their age and size.
Children aged 7 must be secured in a restraint if one is available in the vehicle.
Last month the Herald reported of another case where police had to step in to make sure unrestrained children got home safely.
Constable Mark Wakefield used his own children's car seats to make sure two unrestrained youngsters got home safely after he pulled their father over for speeding north of Auckland.
When the driver stopped Mr Wakefield discovered the man'ss 3-year-old daughter was lying in the back seat and his 18-month-old was in the front passenger seat, which was reclined.
Neither child had a car seat or seatbelt.
Mr Wakefield said they were "very tiny little girls" and he was not willing to let the man drive on with them unrestrained.
He called colleagues at the Warkworth police station, asking them to go to his home and pick up his own children's car seats.
He stayed with the man until the seats arrived, then fitted them into the car and made sure the girls were strapped in before they left the traffic stop.
Mr Wakefield followed the man to Manukau and when he was home safely collected his car seats and went home.
