A French court on Thursday upheld a decision by doctors to withdraw life support for a man kept alive in a vegetative state for a decade, after the latest legal challenge by the patient's parents in a divisive right-to-die case.

Vincent Lambert, 42, was left a tetraplegic after a car accident in 2008, with doctors later determining that his severe brain damage was irreversible.

Under French law, doctors then decided to remove the intravenous food and water keeping Lambert alive, a move backed by his wife and six of his eight brothers and sisters.

But his deeply devout Catholic parents contested the decision, arguing that Lambert's condition might improve if he received better treatment.

That set off years of legal wrangling over the power of French doctors to determine whether a patient in a long-term vegetative state should be kept alive.

French courts have largely sided with Lambert's doctors, prompting his parents to take the case as far as the European Court of Human Rights, which ruled in 2015 that he should be allowed to die.

On Thursday an administrative court in Chalons-en-Champagne near Reims, where Lambert is hospitalised, said that maintaining him alive constituted "unreasonable obstinancy".

"Vincent Lambert's wish not to be kept alive if he was ever in the state he has now been in for 10 years has been established," the court said in its ruling, obtained by AFP.

Lambert's parents had already indicated that if the court ruled against them, they would appeal before the Council of State, France's highest administrative court.

Active euthanasia, by which a person deliberately causes the patient's death, remains illegal in France despite recent efforts to ease legislation dealing with the terminally ill.

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© Agence France-Presse