Prime Minister Tony Abbott has promised a dying man that he will allow Liberal Party members to vote with their conscience on a euthanasia bill being developed by a Greens senator.

Peter Short, 57, said receiving the commitment during a half-hour phone conversation with the Prime Minister on Friday was like reaching "the top of a mountain".

Tony Abbott made a promise to a dying man. Credit:Alex Ellinghausen

Mr Short is preparing to spend his final Christmas with his family after being told in January that his oesophageal cancer – first diagnosed five years earlier – had returned and was terminal.

He has devoted the final stage of his life to campaigning for legislation that would enable terminally ill people to choose when and how they die.