LONDON — A 58-year-old British man suffering from so-called locked-in syndrome died Wednesday, six days after a panel of High Court judges rejected his request for help in ending his life. His death is certain to galvanize the already contentious debate about assisted suicide in Britain.

The man, Tony Nicklinson, a former rugby player and sky diver who suffered a stroke in 2005, died at his home in Melksham, 80 miles west of London, at 10 a.m., according to a statement issued by the law firm that represented him.

Mr. Nicklinson’s family used his Twitter account to say that he died of natural causes. At a news conference, Saimo Chahai, the family lawyer, said Mr. Nicklinson had been refusing food since the court ruling and had declined rapidly over the weekend after contracting pneumonia. “The fight seemed to go out of him,” she said.

After having a stroke while on a business trip to Athens, Mr. Nicklinson, a civil engineer, developed locked-in syndrome, an incurable condition in which a patient loses all motor functions but remains awake and aware, with all cognitive abilities. He had spent the last seven years paralyzed from the neck down and unable to speak, feed himself or even clean his own teeth, communicating through a system that allowed him to write messages on a computer screen by blinking his eyes.