Malnutrition afflicts 70 per cent of older people living at home and is estimated to affect about 45 per cent of Alzheimer sufferers.
Age UK estimates that 1.3 million people over 65 suffer from malnutrition, with the vast majority of those - 93 per cent - living in the community.
Almost 10 per cent of older people living at home are affected by malnutrition, 30 per cent living in care homes and 70 per cent of older people in hospital, according to a report from Alzheimer's Disease International and the Compass Group.
"Consequences include frailty, reduced mobility, skin fragility, an increased risk of falls and fractures, exacerbation of health conditions and increased mortality," said the report.
Health Secretary Jeremy Hunt has said that too many elderly people were ending up in hospital because of the flawed GP contracts introduced by the Labour government.
Mr Hunt told the Daily Telegraph: “Labour’s disastrous 2004 GP contract left many vulnerable elderly patients without good out-of-hours care, so it’s rank hypocrisy for them now to complain about the consequences of their historic mistake.
"We have ripped up that contract and are bringing back proper family doctoring, with named GPs for older people to help relieve A&E pressures.”
He added that they allowed family doctors to abandon responsibility for out-of-hours care.
Age UK has said that some of those admitted to hospital is a consequence of "not getting good quality care at home".
Caroline Abrahams, charity director at Age UK, said: "It is important that older people receive the treatment and care they need and sometimes this means going to hospital.
"However we know that in some cases being admitted to hospital is the consequence of not getting good quality care at home."
Access to high quality social care is increasingly difficult as many vital services are withdrawn or reduced as a result of the current crisis in care.
"The core of the problem is that funding for social care has failed and is still failing to keep up with growing demand. Legislative reform is vital but pointless unless sufficient funding is in place."
Labour said the ambulance figures confirm that cuts to social care funding are driving up the need for hospital attention among the elderly.
Shadow health secretary Andy Burnham said data in the House of Commons library shows that local authority spending on adult social care has been cut by £1.8bn since 2009/10.
He said: "These shocking figures expose the growing crisis in older people's care on David Cameron's watch.
"The Government's severe cuts to social care have left thousands of older people without the support they need - at risk of going into hospital and getting trapped there. It is one of the root causes of David Cameron's A&E crisis.
"It is appalling to think that every week there are thousands of frail and frightened people speeding through our towns and cities in the backs of ambulances to be left in a busy A&E."
The number of very elderly people needing to go to hospital by ambulance has risen 81% since 2009/10, according to new figures.
Analysis by Labour showed that 300,370 people over the age of 90 were taken to A&E by ambulance in the last year, a substantial rise on previous years. In 2009/10 the figure was 165,910.
The data comes from tables of ambulance activity in England published by the Health and Social Care Information Centre (HSCIC).
George McNamara, head 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.
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."
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 report said two-thirds of care homes and hospitals who make applications break the law by failing to notify the CQC of outcomes or applications.
The CQC said this contrasted sharply with people aged 18 to 65 for which the rate has increased much less over the period and fell slightly last year.
Deprivation of Liberty Safeguards, 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. Deprivation could include restraint, medication given against a patients will, staff having complete control over a patient's care or movements and staff making all decisions about a patient.
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.