Road accident victim Paul Lamb and the family of the late locked-in syndrome sufferer Tony Nicklinson have lost a right-to-die challenge at the Court of Appeal.
Judges rejected their appeal against the long-established legal position that voluntary euthanasia is murder.
Former builder and father-of-two Mr Lamb, 57, from Leeds, who wants a doctor to help him die in a dignified way, had won the right to join the litigation to continue the battle started by Mr Nicklinson.
Mr Nicklinson, 58, died at home in Melksham, Wiltshire, in August 2012, a week after he lost a High Court bid to end his life with a doctor's help.
The father-of-two, who was paralysed by a stroke while on a business trip to Athens in 2005, had refused food and contracted pneumonia after he was "devastated" by the decision.
During the appeal hearing the judges heard argument that people who are too sick or disabled to end their "unbearable" lives without help are currently being condemned to "suffer in silence or make desperate attempts to kill themselves".
The ruling was given by the Lord Chief Justice Lord Judge, Master of the Rolls Lord Dyson and Lord Justice Elias.
Mr Lamb said he was "absolutely gutted" by the decision.
He added: "I was hoping for a humane and dignified end. This judgment does not give me that.
"I will carry on the legal fight - this is not just about me but about many, many other people who are being denied the right to die a humane and dignified death just because the law is too scared to grapple with these issues."
