The number of safeguarding applications which deprive old people of their freedom through the use of techniques such as restraint have seen a sharp rise.
A report from the Care Quality Commission (CQC) found a "sharp increase" in the number of applications from organisations such as care homes to deprive people aged 75 and over of their liberty.
For those aged 75 to 84, there was an 81% jump in the number of Deprivation of Liberty Safeguards (DoLS) applications made between 2009/10 and 2012/13, from 71.2 per 100,000 to 128.6
Among those aged 85 and over, the figure jumped 69%, from 156.6 per 100,000 to 265.3.
"This contrasts sharply with the 18 to 65 age group, for which the rate has increased much less over the period and fell slightly last year," the report for England said.
DoLS, which apply in England and Wales, are intended to ensure that a care home or hospital only deprives someone of their liberty in a safe and correct way when they lack mental capacity.
They should only be applied when it is in the best interests of the person and there is no other way to look after them.
Examples of deprivation include a patient being restrained, medication being given against their will, staff having complete control over a patient's care or movements and staff making all decisions about a patient.
Today's report found around two-thirds of care homes and hospitals who make applications are breaking the law by failing to notify the CQC of applications or their outcomes.
It said: "Failure to notify us removes an important element of protection for people subject to the Deprivation of Liberty Safeguards, as well as their families, friends, and the staff and organisations caring for them, by lessening our knowledge of how and where the Deprivation of Liberty Safeguards are being used."
Most applications and authorisations relate to older people with dementia living in care homes. Dementia accounted for 53% of all applications in 2012/13, of which 59% were authorised.
The study said the number of applications has increased every year since the measures were introduced in 2009, though the rate of increase in 2012/13 was smaller than previous years.
There were 11,887 DoLS applications in 2012/13, a 4% increase on the 11,393 applications made in 2011/12.
The number of authorisations also increased, with 6,546 authorisations granted compared to 6,339 in 2011/12.
The CQC said checks on implementation of the Mental Capacity Act (MCA), which covers DoLS, will become a routine part of hospital and care home inspection from now on.
The regulator said people's experiences of DoLS are "mixed" and application rates continue to vary by region, with the reasons for this being unknown
CQC chief executive David Behan said: "We expect more focus on reducing the restraint and restriction of vulnerable people lacking capacity.
"We want to ensure people who are unable to consent to treatment because they lack capacity receive high quality care as a fundamental part of health and care services.
"While there has been an increase in the use of DoLS, there is still much more that needs to be done to ensure people are appropriately cared for.
"This year, CQC is strengthening its approach to monitoring this legislation and we will be working more closely with local authorities to support them in their roles as supervisory bodies."
The study found that, in some cases, people were being deprived of their liberty without legal basis (93 cases in 2012/13) but it is " unlikely that all incidents of unlawful deprivation of liberty have been identified by this process".
Care and support minister Norman Lamb said: "People in hospitals and care homes deserve to be fully protected at all times, particularly when they need to be deprived of their liberty in their own best interests.
"This increase shows that more assessments are being carried out when they should be to safeguard people and protect their rights.
"Yet there is a long way to go before these provisions are fully used.
"The bottom line is that to deprive someone who lacks capacity of their liberty without a DoLS in place is unlawful and needs to be treated extremely seriously."
George McNamara, h ead of policy and public affairs at the Alzheimer's Society, said: " These findings point to a worrying lack of awareness and understanding of the use of DoLS.
"It is unacceptable that the majority of care providers are not following correct procedure when using this measure. Over half the applications were for someone with dementia and much more needs to be done across health and social care to ensure DoLS are better understood and implemented consistently, ensuring the best possible quality of care and support.
"It is essential that the CQC continue to monitor its use to protect those most vulnerable in society."
Paul Farmer, chief executive of Mind, said DoLS can protect people at their most vulnerable.
He said: "We know that confusion persists among staff about how DoLS should be used, and that practices such as restraint may be being overused.
"The widespread variation in the use of DoLS is also of great concern to us and could mean that people's rights are being ignored.
"Closer scrutiny by the CQC is an important step in understanding and tackling these fundamental issues more effectively.
"DoLS play an essential role in protecting the human rights of people who are at their most vulnerable and so it is vital that we understand as much as we can about how and why they are being used.
"Where it is considered necessary to deprive someone of their liberty, individuals and their families must have faith that it is being done in an appropriate and lawful way."
Mr Behan added: "I am pleased to see a rise in the number of applications.
"It is important that people who lack the capacity to make decisions for themselves about their care are protected by the law in this way.
"The use of the DoLS by a care home or hospital demonstrates they are concerned to protect the rights of these very vulnerable people."