Patients who demand the right to life-prolonging treatment will have "very serious implications" for the national health service, appeal judges were told yesterday.

Lawyers for the health secretary, Patricia Hewitt, yesterday intervened in the case and backed the General Medical Council's bid to have a high court ruling from last year set aside.

Leslie Burke, 45, has a degenerative brain condition and last July won the right to stop doctors withdrawing artificial nutrition or hydration (ANH) treatment until he dies naturally.

The ruling was hailed at the time as a breakthrough for the rights of vulnerable patients.

Backing a GMC bid to reverse the ruling, the health department claimed that if a right to ANH was established, patients would be able to demand other life-prolonging treatments.

Philip Sales, representing the health secretary, told a panel of three appeal judges, headed by the master of the rolls, Lord Phillips: "A general right, as identified by the judge in the high court, for an individual patient to require life-prolonging medical treatment, has very serious implications for the functioning of the NHS."

He went on: "It may be interpreted as giving patients the right to demand certain treatments, contrary to the considered judgment of their medical team, that would lead to patients obtaining access to treatment that is not appropriate for them, and to inefficient, and unfairly skewed, use of resources within the NHS."

He said that under current GMC guidelines to doctors, a competent patient was entitled to decide between the treatment options offered to him by his doctor.

However, doctors are not required to give treatment that they believe is not clinically appropriate, or which cannot be offered for other reasons, such as the costs, within the NHS.

Mr Justice Munby ruled in May last year that if a patient is competent, or has made a request before becoming incompetent, doctors have a duty to provide ANH.

Mr Sales said this ruling had led to a confusion between the roles of doctor and patient - the decision about treatment was for the doctor, not the patient.

There was also concern that patients would request treatments no matter how inappropriate or costly.

Mr Burke, of Lancaster, who suffers from cerebellar ataxia, was in court in his wheelchair yesterday listening to the arguments for overturning the ruling which he believes would save him from death by starvation or thirst if ANH is withdrawnafter he loses the ability to communicate.

Richard Gordon QC, for Mr Burke, argued that the case for the GMC was based upon a misunderstanding of the role of doctors in relation to the legally competent patient.

The key issue could be summarised in two words - who decides?

Mr Burke was a legally competent person and wanted to receive food and water administered by artificial means when he had difficulty in eating or drinking.

Mr Gordon said that if the GMC was right, the most that Mr Burke would get was that his preferences would be taken into account, but they might in the end be trumped by a doctor's decision that it was too burdensome for him to continue to live.

The hearing continues.