Families are paying too much for social care "all too often" because they are not getting the correct information, according to a report.
The Local Government Ombudsman (LGO) says many families across England are paying more than they need to because they have not been given comprehensive information about the costs of care in their area.
In the report - titled Counting the cost of care: the council's role in informing public choices about care homes - which looks at "top-up fees" paid by families for relatives' care, the LGO explains the confusion faced by people looking to place a relative in a home.
It gives examples of cases where councils provide confusing or incorrect advice, do not offer potential residents a genuine choice of affordable care homes or have any affordable homes available.
Sometimes when a family member is settled in a home and all costs agreed, providers have tried to charge their own top-up fees without the local authority's consent, the report found.
This confusion can lead to people paying more than they need to.
The report said: "The decision to place a loved one in a care home can be one of the hardest any family has to make, but all too often families are paying too much for their care because they are not getting the correct, timely information."
The LGO provides guidance for councils to make sure their procedures do not put people at risk of paying too much and offers questions for councillors to help scrutinise their authorities' policies and procedures.
Jane Martin, Local Government Ombudsman, said: "When confronted with what can be an emotionally charged decision to place a relative in a care home, people need as much information as possible at their fingertips.
"In order to make the best possible choice for all, families need to have confidence that the information they receive is clear, comprehensive and accurate.
"I would urge all councils to look at the information they provide from the potential resident's point of view to ensure their literature and communications minimise the confusion for those who need advice and help."
There were 2,848 complaints about adult social care (ASC) in the period from August 2014 to July 2015 - up from 2,397 in the previous 12 months.
Of the 2,848 complaints, 57.5% of cases investigated in detail were upheld, the LGO said.