One in every 25 mentally ill patients who have been sectioned have 'irregularities' in their records which could mean they are being unlawfully detained, the health watchdog has warned.
Of 4,500 patient records checked by the Care Quality Commission (CQC) between 2011 and 2012, 4 per cent contained mistakes which called the legality of their detention into question.
The number of people detained under the Mental Health Act is on the rise.
People with mental disorders can be detained to ensure they get the treatment they need for their own health or safety, or for the protection of other people.
In 2011/12 the number of men and women sectioned in England reached 48,600 - a five per cent rise on the previous year.
In its annual Mental Health Act report the CQC also raised concerns that patients were not informed of their right to see a lawyer.
The report says one in five patients were not informed of their right to see an independent mental health advocate.
Officials also said they were worried about cultures where "control and containment are prioritised over the treatment and support of individuals".
The report says: 'The human rights of patients are often affected by controlling practices that only seem to serve the hospital's needs.
"Hospitals have a difficult task in balancing the realities of detention and compulsory treatment with the requirement that they provide services according to a principle of least restriction on patients.
"But it has proved all too easy for cultures to develop in which blanket rules deny people their basic rights - especially the right to dignity."
The CQC said hospitals should ensure there are no 'blanket rules' which deny patients autonomy and dignity.
The health watchdog also said it was worried about the strain on services.
Experts found that one in 16 wards had more patients than beds and 10 per cent were ope"ating at full capacity.
'Pressures on beds continued to put services and patients under stress, making it harder to provide appropriate care for people in times of crisis," the report says.
"In 2011/12, 93 wards (6 per cent of all wards) visited had more patients than beds; a further 10 per cent were at full capacity."
The report added, "Patients are being affected by reductions in staff numbers. For example, Mental Health Act commissioners raised concerns in 77 visits that a lack of staff prevented patients taking escorted leave."
The CQC said mental health services must do much more to ensure the care they provide for detained and non-detained patients in mental health hospitals is based on individual needs.
CQC chief executive David Behan said, "People who need treatment in hospital for their mental health should have care and support to help them recover.
"Some hospitals are doing a very good job in treating people with dignity and respect - so we know it's possible.
However, CQC is concerned that some hospitals have allowed cultures to develop where control and containment are prioritised over treatment and care.
"This applies as much to detained patients as well as to those who are receiving treatment on a voluntary basis.
"In fact it is even more important people can be compulsorily treated - greater attention needs to be paid to ensuring as much dignity and choice as possible is promoted. Boards, providers and commissioners of service need to ensure that the proper safeguards and care practices are available to patients.
"Our report has found too many instances where people have been restricted inappropriately. It is unacceptable for the current situation to continue.
"All patients, whether detained under the Mental Health Act or not, need to be involved in their own care and consulted on their own wishes and desires. Clinical staff must be trained in assessing and recording patients' capacity and consent."