Dementia sufferers are likely to experience poor care as they move between residential homes and hospitals because of an "unacceptable gap" in quality, a damning new report says.
Nine out of 10 units assessed by the Care Quality Commission (CQC) were found to have some aspects of poor care, it said.
It criticised hospitals for focusing too much on patients' physical needs and said both hospital and care home staff had "a lack of understanding and knowledge of dementia care" and poor sharing of information.
Andrea Sutcliffe, the CQC's chief inspector of adult social care, said: "People living with dementia, their families and carers have every right to be treated with respect, dignity and compassion.
"Our review found some great care, delivered by committed, skilled and dedicated staff. But this is not the case everywhere or even within the same service meaning too many people are at risk of poor care. This has got to change."
The CQC inspected care in 129 care homes and 20 hospitals across England, looking at four areas: care assessment; planning; how providers worked together; and how the quality of care was monitored.
It said that in about 29% of care homes and 56% of hospitals, care assessments did not identify patients' needs. Thirty four per cent of care homes and 42% of hospitals were found to be giving "variable or poor" care.
It also found that known risks to patients like falling over, urinary tract infections and malnutrition were not being managed properly.
The CQC said it planned new measures, including appointing a new national specialist adviser for dementia care, more training for inspectors to "understand what good dementia care looks like" and ensuring a consistent level of judgments and adding a separate section in hospital inspection to focus on patients with dementia.
Jeremy Hughes, chief executive of the Alzheimer's Society, said: 'With a staggering 90% of the care homes and hospitals inspected found to have aspects of variable or poor care, this report highlights the plight that many people with dementia face.
"The inconsistency of care found here means many people are rightly worried about being admitted to hospital or having to move into care. Carers have told us that their loved ones have gone for hours without food or water in hospital or that they were in pain but no one realised.
"Staff can also find communicating with people with dementia extremely challenging and wards and a new care home can be disorientating to navigate.
"However, we know there are many care homes and hospitals that are getting it right by training their staff in person-centred care and making their homes and wards more dementia friendly. Developing staff and helping them understand the needs of people with dementia is vital if we are to improve the care people receive."
Health Secretary Jeremy Hunt said: "There can be no excuse, and no hiding place, for poor care within our NHS - we are focusing on improving the lives of dementia patients and their families as never before. That's why we've trained thousands of NHS staff to recognise the signs of dementia and invested in dementia friendly care homes and hospital wards.
"The CQC play a vital role in improving care through their tough new inspections and it's vital that they continue to shine a light on any poor practice so that we can drive up standards throughout the country."