Mental health bodies have raised concerns over revelations that thousands of mental health patients are being locked in "effectively institutionalised settings".
A new Care Quality Commission (CQC) report has highlighted that a "surprising" number of patients are being cared for in "locked rehabilitation wards", with some patients spending more than four years in such facilities.
CQC said a "significant number" of patients treated on such wards could have been cared for in lower dependency settings with fewer restrictions.
The CQC found there were more than 3,500 beds across 248 locked mental health rehabilitation wards in England. About two-thirds of these beds were managed by independent care providers.
The report highlighted that some patients appeared to be spending "longer than would be expected" for a rehabilitation service.
In 2015/16 the average length of stay for patients on high dependency rehabilitation wards was 341 days. This ranged from 45 days to 1,744 days.
The report stated: "Our inspectors were concerned that some of these locked rehabilitation hospitals were in fact long stay wards that risk institutionalising patients, rather than a step on the road back to a more independent life in the person's home community.
"We do not consider that this model of care has a place in today's mental health care system."
The CQC report, which analysed the state of mental health care across England between 2014 and 2017, also raised a series of concerns about mental health provision. These include:
:: Long waiting times for memory clinics for dementia and eating disorder services;
:: Some mental health crisis teams do not provide 24 hour cover;
:: A shortage in mental health nurses - from January 2010 to January 2017 the number of nurses specialising in the field fell by 12%;
:: The "unavailability" of inpatient care for young people with mental health problems. The authors highlighted a case of a 17-year-old who was kept in a police cell for 78 hours because no bed was available;
:: Concerns were raised over safety with two in five (40%) NHS services rated as either "requires improvement" or "inadequate" in this area. Issues included inadequate facilities to care for patients, safe staffing levels and the management of medicines;
:: Inspectors found a "great variation" on how much physical restraint was used against patients. In some wards, staff are able to avoid the use of restraint to anticipate or de-escalate behaviours or situations which could lead to aggression or self-harm.
"There are signs of a system under pressure," said Paul Lelliott, the lead for mental health and deputy chief inspector of hospitals at the CQC.
"We are concerned about what are called locked rehabilitation wards. The Royal College of Psychiatrists doesn't recognise this as a model of care.
"We were surprised at just how many of these wards there were and how many were locked.
"To our surprise we found that there were 3,500 beds on locked rehab wards. These wards are often a long way from people's homes.
"We also had some concerns about the fact that they weren't that discharge oriented, they weren't actively enabling people to return back to their home environments.
"If these wards are rehabilitation wards they should be working actively to re-engage people with their communities and we think given the number of wards that we found, that many of the patients in these wards don't need to be in a locked ward and could and should be moved back to their home area where they can receive intensive support in a community setting."
But Mr Lelliott highlighted that a high proportion of organisations were rated as good or outstanding for being caring.
Mental health charity Mind said there were "pockets of disturbing information" in the report.
Sophie Corlett, director of external relations at the charity, said: "There are some quite worrying things in here from the point of view of people receiving services, some that you would really not expect to be seeing in 2017.
"We have had many years of knowing that being in long-stay, locked accommodation is of no use to you, is expensive to the nation and is a human rights abuse, effectively to take away your liberty and to give you no therapeutic future.
"To see that there are 3,500 people in effectively institutionalised settings in 2017 is very worrying."
Claire Murdoch, NHS England's national director for mental health, said: "We have already made huge steps forward in improving mental health care nationally, overall mental health funding is up by £1.4 billion in real terms and 120,000 more people are getting specialist mental health treatment this year than three years ago.
"It's pleasing to see that the report identifies that mental health services have the raw material to deliver great things and that almost every service was rated as good or outstanding for care.
"We know that there is more work to do which won't happen overnight, this is why we have a five year plan in place to ensure that transformation is under way so that we can consistently and quickly deliver the best possible care at the right time and importantly, in the most appropriate location, for those who need it."
Dr Adrian James, spokesman for the Royal College of Psychiatrists, said: "We are pleased that the CQC's report identified a high level of mental health services providing world-class care and it's heartening to see, that despite the pressures on mental health services, staff are providing outstanding levels of care for patients.
"But equally it's concerning that many patients are being held for too long in locked wards miles from their families."
A Department of Health spokesman said: "As this report identifies, there are many examples of excellent mental health care and nearly all services were rated as good or outstanding for having caring and compassionate staff.
"But we know there is more to do to promise everyone the very highest standards of care – that's why we are undertaking probably the most widespread programme of mental health transformation in Europe, supported by our rigorous inspection regime and £1 billion more investment for mental health by 2020."