Patients with mental health problems, autism and learning disabilities are being let down by a "broken" care system, a report warns.
The Care Quality Commission (CQC) says it knows of at least 62 adults and children that have been living in segregation in mental health hospitals for long periods of time.
Health Secretary Matt Hancock, who commissioned the work, said he was appalled by the distressing stories.
He promised cases would be reviewed.
The report presents the CQC's initial findings on the use of long-term segregation on mental health wards for children and young people and wards for people with a learning disability or autism.
The CQC has so far visited and assessed the care of 39 people in segregation - most had a diagnosis of autism.The 62 cases identified (after contacting 89 registered care providers) include 20 children and young people, some as young as 11 Many of the patients had been placed in hospitals miles away from home Some had spent years in hospital, separated from other patients and staff Patients risked becoming stuck in segregation
The most common reason given for segregating was to keep other patients safe or a belief the patient would be unable to cope around others.
The CQC found some of the wards were not suitable environments for people with autism and many staff lacked the necessary training and skills to work with patients with complex needs and challenging behaviour.
Some of the hospitals visited had "features of institutions that are at risk of developing a closed and even punitive culture".
In the case of 26 of the 39 people, staff had stopped attempting to reintegrate them back in to the main ward environment, usually because of concerns about violence and aggression.
Often, a suitable alternative place of care, such as a community placement, could not be found.
Dr Paul Lelliott, of the CQC, said: "The people we have visited have had contact with health, care and education services for many years, pointing to missed opportunities that may have prevented admission to hospital in a crisis because there was nowhere else for them to go.
"These people have been failed by the current system of care and that system must be changed."
Mr Hancock said: "At its best, the health and care system provides excellent support to people, backed by a dedicated workforce.
"But a small proportion of some of the most vulnerable in society are being failed by a broken system that doesn't work for them. They deserve better."
He said the government would fund specialist, independent advocates to work with families, join up services and try to move people to the least restrictive care and then out into the community.
Rebecca Hilsenrath, of the Equality and Human Rights Commission, said: "We welcome the CQC's call for urgent action and we are looking at what more we can do to ensure those in the most vulnerable situations get the care they need close to home.
"This must include people with learning disabilities and autism in mental health hospitals."