Too many hospitals in England are falling short in the most basic care they are giving elderly patients, inspectors say.
The Care Quality Commission carried out unannounced visits at 100 hospitals to assess dignity and nutrition standards.
It identified concerns in 55 cases, describing the findings as "alarming".
Common areas of concern included a lack of support for those who needed help eating, poor hygiene and curtains not being closed properly.
Health Secretary Andrew Lansley said he would encourage whistle-blowers to highlight any concerns they had about the standard of hospital care for the elderly.
He said: "We expect that staff across the NHS, if they see examples of poor care they blow the whistle on that, which is precisely why we have introduced changes to the staff contract."
The inspections were ordered by Mr Lansley after several highly critical reports by campaigners, including the Patients Association.
The 100 sites inspected - representing more than a third of the total number in England - were chosen through a combination of random selection and because previous research had flagged up concerns about standards.
In total, 45 were judged to be fully compliant, 35 met both the official standards on dignity and nutrition although there was room for improvement and 20 were failing on one or both.
In two cases - Sandwell General in West Bromwich and Alexandra Hospital in Worcestershire - the problems were judged to represent a major problem to patients.
In the case of Sandwell, this led to the closure of the ward where there were the most problems, while a follow-up visit to the Alexandra showed measures had been put in place to rectify the issues.
At another - James Paget in Great Yarmouth - moderate problems were identified, but when a return visit was made and the issues had not been resolved the hospital was issued with a warning notice, meaning if swift improvements are not made it could face sanctions including prosecution or closure of services.
During the inspections, the regulator identified a series of common problems.
These included call bells being placed out of the reach of patients, staff speaking in a condescending or dismissive way and curtains not being closed properly.
In terms of nutrition, some people who were judged to need help eating were not getting it, while interruptions meant that not all meals were being finished by patients.
The regulator also said that in too many cases patients were not able to clean their hands before meals.
The report identified three main reasons for the failures - a lack of leadership, poor attitude among staff and a lack of resources.
CQC chair Dame Jo Williams said: "The fact that over half of hospitals were falling short to some degree in the basic care they provided to elderly people is truly alarming and deeply disappointing. This report must result in action."
Michelle Mitchell, charity director of Age UK, agreed.
"This shows shocking complacency on the part of those hospitals towards an essential part of good healthcare and there are no excuses."
Janet Davies, of the Royal College of Nursing, accepted there could be "no excuse", but added the squeeze in finances was making it harder to keep standards high on wards.
"Evidence shows that patient safety and quality of care is improved when you have the right numbers and the right skills in place on wards," she added.
Both the government and the NHS Confederation, which represents managers, said examples of poor care were "unacceptable".
Mr Lansley added: "Everyone admitted to hospital deserves to be treated as an individual, with compassion and dignity. We must never lose sight of the fact that the most important people in the NHS are its patients."