Over half of the British public want a change in the law to stop doctors from being able to withdraw water from patients.
Currently, under the Mental Capacity Act, doctors are permitted to allow patients to die from dehydration if they believe it is in the patient's "best interest" and that death may occur soon.
In an online ComRes poll of 6,130 UK adults commissioned by anti-euthanasia charity Alert, 58% said they believed the law should be changed to stop this if the patient had expressed a wish to remain alive while they still had the capacity to communicate.
Seventeen per cent said they wanted no change in the current law, while 25% said they lacked an opinion.
Among the disabled and those aged 65 or above, the numbers supporting a change in the law to stop medical water withdrawals rose to 61% and 62% respectively.
Under a 1993 Law Lords ruling, food and fluids were classified as "treatment" and therefore they could be withdrawn by doctors for patients in a vegetative state, as in the case of Tony Bland, a victim at the Hillsborough football disaster in 1989.
While the Mental Health Act of 2005 allowed patients to draw up contracts ordering doctors to withdraw food and fluids upon incapacitation, no provisions were made for the opposite arrangement.
Speaking about the poll, Baroness Campbell of Surbiton said: "Food and water are basic human rights. They should never be withheld merely because a patient is mentally incapacitated or believed to be near to the end of life.
"This research confirms what disabled people have telling me for some time. Many are fearful that, if and when they lose capacity, food and water may be denied to them. They, their relatives and friends, need to know that, when they need it most, they will have the full protection of the law."
Alert said today that allowing the current state of affairs to continue would allow abuses of the kind seen under the widely discredited Liverpool Care Pathway (LCP).
The LCP was intended as a system where after a multidisciplinary medical review, doctors would decide if certain non-essential treatments would be given for patients where all medical options had been exhausted.
In practice, the LCP was poorly regulated. Many decisions to remove care were made by non-doctors, and in almost half of cases neither the patient nor their families were informed that they had been placed on the LCP procedure.
In the case of Andrew Flanagan, a 48-year-old patient from Norfolk who had been declared as medically 'dying', the judgement was premature as he was successfully revived five weeks after doctors placed him on the LCP.
In July 2013 it was announced that the LCP would be phased out over 6 to 12 months.
Elspeth Chowdharay-Best, honorary secretary of Alert, said: "The Mental Capacity Act was what lay behind the Liverpool death pathway. It needs to be amended."
Chairman of the Medical Ethics Alliance, Dr Tony Cole, said: "Some of the most distressing cases involving the Liverpool Care Pathway were deaths taking place after prolonged periods of fluid deprivation.
"Thirst is one of the most basic sensations experienced through the thirst centre deep in the brain. The administrations of morphine or other sedatives, does not relieve it but may render the person more helpless. It is time the mantra 'the dying do not experience thirst', is re-examined."
Nikki Kenward of the Distant Voices disability rights group, added: "If you were like I was, paralysed, completely immobile, using all my energy to stay alive, I know that water is not going to be a priority for you.
"Why? Because you just won't know that you're about to be denied it. If your life is seen as not of worth, or as with the 1,200 disabled people who die unnecessarily every year.
"Or because you're old, have dementia, look depressed, or are just in the way of your family's inheritance, you might be looking into that chasm and hoping some decent person passes you the glass or hooks you up before you fall in, be careful, it's a long way down my friend."