A four-year-old boy spent the night with his mum's dead body after police failed to treat a 999 cry for help with enough urgency.
Georgina Beevers, 37, was found dead from a tablet overdose when her son opened the door to officers in the morning - 13 hours after her mum Sheila raised the alarm.
The Manchester Evening News reports that another officer had knocked on the door seven hours earlier but left when there was no answer because he missed the part of the incident log saying Georgina was suicidal.
Sheila, who lived too far away from her daughter to go herself, made a series of calls to police and social services, said: "If they had gone round in the first two hours, as they should have, she would still be alive.
"The one night I needed the help of police and social services they did nothing. I had told them my daughter threatened suicide yet there was no line of communication."
Police watchdog The Independent Police Complaints Commission found the 999 call handler recognised the call needed an immediate response, but a radio operator asked for it to be downgraded. Police were still expected to respond within an hour.
But a robbery and a missing person meant the first officer was delayed getting to the house in Bredbury, Greater Manchester. Not realising Georgina's life was at risk, he left when he got no answer and suggested another officer should go back in the morning.
IPCC chief Naseem Malik said: "This was an incident that needed a priority response. It didn't get one due to flawed decision-making and a lack of diligence."
One officer has since received management action from Greater Manchester Police.
Assistant Chief Constable Zoe Sheard said: "We will continue to work with the family to provide whatever support or assistance we can and are also supporting those officers and members of staff who were personally affected."
A coroner last week recorded a verdict of death by misadventure over Georgina's death in January last year.