About 50,000 people with dementia will be forced into care homes early because of a lack of support in their own homes, experts have warned.
Most people with dementia would prefer to live in the community yet there is inadequate help with everyday tasks such as shopping, washing and dressing, according to a report.
The study, from the Alzheimer's Society, said thousands of people with dementia are admitted to hospital or care homes when they could be supported at home.
For each "avoidable" month these people spend in care homes, the state will face a bill of at least £70 million, the study said. Care homes cost an average of about £559 per week.
There are 750,000 people living with dementia in the UK, two thirds of whom live in their own homes, with the remainder living in care homes.
For the study, the charity received responses from almost 1,400 carers of people with dementia and 48 people living with the condition. Another 989 care home workers also provided information to the charity.
The results showed that 83% of carers thought being able to live in their own home was very important to the person with dementia.
However, 50% reported that the dementia patient was not receiving sufficient support and care to meet their needs. This can lead to early admission to long-term care and avoidable in-patient stays in hospital.
The report said: "Current hospital and long-term care costs resulting from dementia are unsustainable and represent a significant opportunity for resources to be used more effectively while achieving better outcomes."
Carers also reported being under stress, suffering depression and having illnesses themselves.