Europe's top human rights court has allowed doctors to stop treatment of a French man left comatose after a car accident seven years ago, a case that has drawn nationwide attention amid debate about end-of-life practices.

The European Court of Human Rights on Friday confirmed a decision by a French court last year that Vincent Lambert had been clear he did not want to be kept in a vegetative state.

The court's ruling said withdrawing artificial nutrition and hydration would not violate the European Convention on Human Rights.

Lambert's family members disagree on whether to keep him alive artificially. His wife wants doctors to stop life support for him but his parents disagree.

"There's no relief, no joy to express. We'd just like his will to be done", Lambert's wife Rachel said following the ruling of the Strasbourg-based court.

The lawyer for Lambert's parents, Jean Paillot, expressed "great disappointment" and called on doctors to reassess Lambert's condition and "make a new medical decision", stressing that the initial decision had been taken in January 2014.

"We'll continue to fight", said Lambert's mother.

Euthanasia, which involves an act to kill the patient, is not legal in France. But end-of-life legislation allows doctor to stop treatments in certain cases, following a complex process that includes consultation with the family.

Vincent Lambert's case has prompted political movement on the issue.

A new bill, backed by the Socialist government, is currently under discussion in Parliament to allow doctors to keep terminally ill patients sedated until death comes.

Terminal or palliative sedation doesn't actively kill patients. It involves medicating patients until they die naturally of their illnesses or until they starve.

But critics say it means patients can be sedated for weeks before they die and that it may be more humane to opt for euthanasia.

All recent polls have shown that a large majority of French people favour legalising euthanasia.

Euthanasia is currently legal in the Netherlands, Belgium and Luxembourg.