The pensioner, believed to be from Nottinghamshire, was sent to The Old Rectory care home in Saxilby, Lincolnshire, in summer 2019 after arriving from hospital for interim care.
Nottinghamshire County Council agreed on funding for him to remain there as a long-term resident.
However, about a year later he was unexpectedly admitted to hospital before the council received a referral letter stating concerns over the care he received.
Because the care home was not in Nottinghamshire, a safeguarding assessment was conducted by Lincolnshire County Council.
Assessments found the man suffered “substantive injury” during the 12-month stay in the home and was caused “serious but unintentional neglect” due to failures over his care plan.
It was found staff failed to give him “appropriate food and drink”, did not identify his injuries, and the assessment recommended disciplinary proceedings for staff at the home.
The Old Rectory self-referred to the Care Quality Commission before launching both internal and external investigations, as well as disciplinary action against at least four staff members.
In a separate statement, the home confirmed a number of staff members have been dismissed and reviews of its practice have taken place.
A report by the Local Government and Social Care Ombudsman was reviewed by Nottinghamshire County Council on Thursday, November 11.
It found the man, named only as Mr Y, suffered an injured and bleeding toe and toenail, pressure sores, swelling from head to toe on his right side, 23 skin tears, a high temperature and possible dehydration while at the home.
In its assessment, the ombudsman accepted the care provider admitting it was at fault but deemed its care caused “significant and avoidable harm” to Mr Y.
The ombudsman did not find the council at fault, though it recommended the authority arrange for The Old Rectory to provide a “suitable apology” to Mrs Y.
The home has insisted it has issued an apology, but the report says Mr Y’s relative “has not seen this” and therefore another should be sent.
It added the council should issue its own apology, setting out actions taken or due to be taken via its role as the safeguarding authority.
The council was also told that, when receiving a safeguarding enquiry about someone placed in an out-of-county home, it should “follow up to ensure it is involved where appropriate”.
The report adds the authority should ensure it “receives information about what happened” so it can properly support the person and their family.
These recommendations have been agreed upon by the council.
Commenting in Thursday’s governance and ethics meeting, Coun Michael Payne (Lab), who represents Arnold North, described the report as a “shocking read”.
He added: “It must have been a horrific situation for the family.”
Coun Philip Owen (Con), chairman of the committee, added he was “quite shocked” when reading the ombudsman report.
He said: “I know we as a council were not directly involved, but I remain concerned that we [should] follow up safeguarding enquiries about one of our residents as soon as possible.
“We’ve heard assurances this will not happen again in the future.”
A spokesperson for The Old Rectory issued a statement describing it as an “isolated case”, outlining action it has taken since the investigation.
They said: “The home’s management ensured that the correct authorities were immediately informed of the issues as soon as they became aware of the incident and swiftly appointed external investigators to conduct a thorough review.
“As a result of that review, some members of staff were dismissed.
“As the ombudsman’s report has acknowledged we acted promptly, issued an apology to the family and have taken robust steps to stop similar problems happening in the future.”