Sheffield Council has launched a safeguarding review after a woman died following an error.
Carol Leesley died in April last year of natural causes, but concerns about her care were raised at an inquest which concluded in December.
During the inquest, it emerged that a GP had made a safeguarding report just under two months before she died but the council had failed to act upon it.
David Urpeth, assistant coroner for South Yorkshire, has now written to the council asking it to take action to prevent future deaths.
"During the course of the inquest the evidence revealed matters giving rise to concern. In my opinion there is a risk that future deaths will occur unless action is taken," he states in his report.
He goes on to say an automated acknowledgment of the GP's safeguarding report was generated, but it was not acted upon, adding 'it was unclear whether this was a case of unanimous error or IT error'.
Mrs Leesley died at Northern General Hospital of septicaemia and a urinary tract infection. There is no suggestion in the coroner's report of any problems with the care she received at the hospital.
The nature of the safeguarding report is not mentioned by the coroner and the council said it could not provide further details due to patient confidentiality.
Phil Holmes, director of adult services at Sheffield Council, said: "Our thoughts continue to be with the family of Mrs Leesley, who sadly died last year.
"We take issues around safeguarding extremely seriously and, while the coroner found that Mrs Leesley's death was due to natural causes, we are currently reviewing the actions that we took and will ensure that any areas for improvement are promptly acted upon."
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