She said it was not considered euthanasia to abide by a patient's right to refuse treatment or if treatment to alleviate symptoms had the unintended consequence of hastening death.
She said the society agreed with the Medical Association's position on euthanasia, which was that doctor-assisted suicide or euthanasia was unethical - and even if it was legalised it would continue to be unethical.
Hospice NZ Medical Adviser Sandy MacLeod said Mr Key's comment was misguided and incorrect.
She said stopping treatment which was no longer effective was not euthanasia, and prolonging such treatment could increase suffering and distress.
"It appears the Prime Minister has confused the ceasing of curative treatments with ending a person's life. In situations like this people are in fact dying from an advanced disease, not from the withdrawal of the treatment."
Labour MP Maryan Street, who has a member's bill to legalise euthanasia, said palliative care doctors did make decisions that could hasten death.
"There are end-of-life situations that occur in hospitals or hospices all the time. Palliative care specialists and other physicians deal with these issues on a daily basis. There is no doubt that there are times when to run off a life support system or to administer another morphine dose would quite possibly result in the death of a patient."
However, that was a different issue from giving a patient the right to request assisted suicide at a time and by a method of the patient's choosing, which was what her bill proposed.
She said she was not surprised at the stance of the Society of Palliative Medicine because physicians had a long-standing ethical obligation to use their skills to heal. Her bill did contain provisions to ensure doctors were not put under undue pressure.
Mr Key has expressed support for euthanasia and voted in favour of former NZ First MP Peter Brown's Death with Dignity bill in 2003, which failed to pass by a narrow margin. He has not decided whether to support Ms Street's End of Life Choice Bill, which is in the members' bill ballot but has yet to be drawn.