A mentally ill man was found to be two stone underweight with rotten teeth after being left to live on his own.
An investigation into Bedford Borough Council and South Essex Partnership University Trust found the authorities had worked to keep him in his own home at a cost to his health and welfare.
The joint investigation by the Local Government Ombudsman and Parliamentary and Health Services Ombudsman said he was not properly assessed on whether he could make decisions for himself.
The man, who is in his late 50s and has paranoid schizophrenia, lived alone in a flat but got regular visits from social and health workers.
His sister and their parents first raised concerns over his health in 2008, and for the next three years the support team reviewed his situation, but family members remained worried.
The authorities assessed the man as being able to make decisions about his accommodation and finances, but no assessment was made about his ability to manage food, personal care or oral health.
A support package was put together but there was confusion between the council and the trust over the amount of care the man was receiving.
He moved into supported living in December 2011 and his condition has improved.
The report found the council and trust failed to provide proper care and support for the man. Support workers did not visit regularly enough, did not encourage him to attend to his oral health or adopt a healthy lifestyle. There was also a delay in seeking supported accommodation.
Parliamentary and Health Service Ombudsman Julie Mellor said: “This vulnerable man was left living in squalor because he did not receive the care he was entitled to.
“As a result, he was underweight, his teeth were rotten and his bedclothes hadn’t been washed in months.
“At one point his family were so concerned, they brought him to live with them.”
The ombudsmen recommended the council and trust should address the failings, apologise to the man and his sister, and make a payment.
A spokesman for the council and trust said: “We will make a joint payment of £2,000 to the person affected, and a further joint payment of £500 to a family member of the person affected, in recognition of the distress and inconvenience caused.”