Nine out of 10 nurses say they do not always have time to help ensure hospital patients eat properly, a study has found.
Proper nutrition can aid the healing process
The charity Age Concern believes this could be one reason why six out of 10 older patients are at risk of becoming malnourished while in hospital.
The charity said the NHS was continuing to fail patients despite guidelines which make feeding a core priority.
Malnutrition is estimated to cost the UK over £7.3bn a year.
The Age Concern campaign calls for:
Views of patients, and their carers to be considered
Ward staff to become 'food aware'
Older patients to be assessed for malnutrition on admission, and regularly during their stay
Introduction of protected mealtimes
Implementation of a 'red tray system'
Malnourished patients stay in hospital for much longer, are three times as likely to develop complications during surgery, and have a higher mortality rate.
It is a problem which particularly affects the elderly: patients over 80 admitted to hospital have a five times higher prevalence of malnutrition than those under the age of 50.
In 2004 the Department of Health issued core standards for the NHS which commit trusts to providing patients with a balanced and nutritional diet.
This was followed earlier this year by guidance from the National Institute for Health and Clinical Excellence designed to help the NHS identify patients who are malnourished or at risk.
However, Age Concern said despite this malnutrition in hospitals continues to be "all too prevalent" - because too often policy is not being put into practice.
The charity is launching a campaign - Hungry to be Heard - to raise awareness of the problem.
Gordon Lishman, Age Concern director-general, said: "Hospitals are in danger of becoming bad for the health of older people.
"The majority of older patients are being denied some of the basic care they need, leaving hundreds of thousands malnourished.
"Food, and help with eating it, should be recognised by ward staff as an essential part of care, and they should be given time to perform this task."
Age Concern is calling for protected mealtimes during which all non-urgent activity is suspended.
It also backs a system where vulnerable people get their food served on a different colour tray to enable staff to easily recognise who needs special help at mealtimes.
Pauline Ford, Royal College of Nursing advisor for older people, said the survey underlined that, for many nurses, time had become a luxury.
She backed the call for protected mealtimes, and a red tray system.
And she said nurses who were worried there were not enough staff on wards to help patients eat and drink should notify their manager immediately.
"It is unacceptable if patients are not getting the help they need.
"Nurses desperately want to be able to give the standards of care they were trained to give, but need the support and resources to do so. Most importantly they need to be given the time to care."
Public Health Minister Caroline Flint, said improvements were being made - but admitted there were still problems.
She said: "Seventy per cent for example of our hospitals do organise preferred meal times.
"But having said that there are still too many cases where individuals are not being supported and we have to stop that, we can't tolerate that."
A Department of Health spokesperson said a summit on how best to improve care of older people was planned for the autumn.