When staff found the woman she was breathing but unresponsive.
It was only after staff re-entered the cell, they noticed the sock around her neck and called an ambulance. The woman was later sedated and placed in intensive care. She was discharged from hospital two days later.
On November 18, the woman was again arrested and put in a cell with another woman prisoner.
After 30 minutes the call button was activated by the other prisoner. However, as officers didn't notice the activation they didn't turn up for several minutes.
She again did not appear to be breathing and had her bra wrapped around her neck.
She was taken to hospital and later discharged by medical and psychiatric staff into the care of Corrections staff.
Authority chair Judge Colin Doherty said they identified "a number of failings by police staff" including poor communication, the quality and accuracy of their risk evaluations and levels of monitoring.
"It is evident that in both instances police did not sufficiently fulfil their duty of care to her."
Counties Manukau Superintendent Jill Rogers said police accepted the report's findings.
"In these two instances we clearly did not provide the duty of care that is expected when monitoring people being held in our custody unit, particularly those individuals identified as being at-risk.
"This is obviously disappointing and we acknowledge that there were several shortcomings identified by the police staff involved in these two incidents."
The incidents had been investigated and police had identified "learnings where we can
improve our practices".
"Since this incident we have notified the IPCA that we are subsequently in the process of implementing a plan to improve the way staff evaluate and monitor individuals held in our custody unit in order to prevent this from happening again."