Leading doctors say some dying patients are inappropriately being given stomach tubes for feeding.
Inserting a feeding tube is an invasive procedure
New guidelines from the Royal College of Physicians (RCP) say every effort should be made to maintain eating and drinking by mouth.
One expert said tube feeding for people with advanced dementia was often "unnecessary, unethical and dubious" because it did not prolong life.
But a group representing care homes doubted the scale of the problem.
They said there was no evidence that inappropriate tube feeding was "a widespread issue".
Doctors described the insertion of a stomach feeding tube as an invasive procedure, which carried a significant risk of infection and even death.
They said feeding difficulties were a "growing problem" on hospital wards and in care homes, because of the rising number of dementia patients.
A survey suggested that, in 2007, 39,000 people in the UK, not including those in hospital, were being artificially fed. A third of them were living in nursing homes.
Other research by doctors who reviewed medical records suggested that one in five cases of tube feeding was "futile".
The latest report - published jointly by the RCP and the British Society of Gastroenterology - was commissioned because doctors and other staff felt "continuing unease" about feeding problems.
Dr Rodney Burnham, co-chairman of the working party that put together the report, said: "We always have to consider the patient first - and ask: 'What are we trying to achieve?'
"Tube feeding may be appropriate in some circumstances, but the House of Lords has emphasised that it's a medical treatment.
"So consent is necessary, and it must be medically appropriate.
"Oral feeding should be the main aim, because it provides comfort and pleasure to patients, and improves their quality of life."
Dr Burnham said feeding tubes should not be used for the convenience of staff, or because they were worried about being sued.
The report says all NHS trusts and care homes should ensure there were sufficient staff, especially at meal times.
Dr Burnham added: "Some care homes may insist on a stomach tube before people are considered for admission.
"This may ostensibly be on the grounds of safety - but there could be a hidden agenda on the grounds of costs or staff not having time to help with feeding."
The English Community Care Association, which represents 5,000 care services, denied the claims.
Martin Green, the chief executive, said: "I'd like to know the evidence for this. I don't think it's a widespread practice.
"If people have examples of this, they should let regulators at the Care Quality Commission know.
"Tube feeding isn't an easy option for staff, because of the risk of infection. Inserting a tube would be a decision taken by a doctor, not a care home."
The Alzheimer's Society said: "It is completely unacceptable that a lack of dementia training could be contributing to the current use of artificial nutrition.
"It is essential that dementia training becomes a mandatory requirement for all care home staff."
A Department of Health spokesperson said: "The use of intrusive interventions, such as tube feeding, is a clinical decision and should only be used when necessary, based on the circumstances of the person concerned, and with their or their representative's agreement.
"We would expect services to allow maximum choice and control wherever possible and to respect people's dignity and human rights right up to the end of life."