The parents of Tony Bland, 21, who has been unconscious since 1989, have repeatedly asked for him to die with dignity, but have seen their wishes denied by an area of the law that is unclear.
Mr Bland's doctors at Airedale Hospital, near Keighley, West Yorkshire, fear that they could be prosecuted for murder if they stop giving him food and water.
His condition is known as persistent vegetative state which, according to most experts, leaves no hope of recovery but the possibility that he could survive for another 30 years. Although he breathes normally, higher brain functions have been destroyed. About 1,500 people are believed to be in this state.
Yesterday, Yorkshire Regional Health Authority said that it had consulted legal experts on the possibility of bringing a test case.
It said: 'We are very sympathetic towards this young man's family. Clarification of this important ethical question would be not just for the benefit of Mr Bland's family, but hundreds of relatives of other patients with the persistent-vegetative state.'
If such an action went ahead, it would raise difficult ethical and legal issues, the crucial one involving a decision on whether the feeding tubes constituted treatment, lawyers said yesterday.
At present, the courts accept that doctors can allow patients to die where there is no hope of recovery and they are kept alive only by medical treatment.
'But is, in fact, feeding somebody down a tube medical treatment?' Dr Kate Allsopp, of the Medical Defence Union, said. 'You can argue that this is a hotel facility. The law is not clear.'
However, Andrew Grubb, reader in medical law at King's College, London, said that there was no difference 'in principle or logic' between withdrawing treatment and disconnecting feeding tubes to a patient in persistent vegetative state. The only arguments against such an action would be based on emotion, he said.
He said: 'My best judgement is that the courts will say that it is lawful to disconnect provided that the doctors have reasonably come to the view that it is truly a persistent vegetative state.'
He said, however, that some medical experts believed that the condition could be treated, particularly in its early stages.