Euthanasia is already happening in New Zealand hospitals, according to Prime Minister John Key.

Mr Key has said he "broadly supports" the principle of voluntary euthanasia, and would consider it if he were terminally ill himself.

Labour Party MP Maryan Street's End of Life Choice Bill would legalise euthanasia, and it's created controversy even though it's yet to be drawn from the ballot.

The Prime Minister said he has not read Ms Street's member's bill, so has not completely decided how he would vote if it were drawn.


John Key voted in favour of a similar bill from NZ First MP Peter Brown in 2003.

"I'd just look at it and say - if I had terminal cancer, I had a few weeks to live and I was in tremendous amount of pain, if they just effectively wanted to turn off the switch, and could legalise that by legalising euthanasia, I'd want that," he told Newstalk ZB yesterday.

Mr Key said he understands the argument legalising euthanasia could put pressure on the elderly to end their lives early, however he did not buy into it.

"I think there's a lot of euthanasia that effectively happens in our hospitals."

However the director of the Association of Salaried Medical Specialists, Ian Powell, did not think euthanasia was occurring the way Mr Key made out.

"The situation is much more complex than that," he told Fairfax Media.

"Sometimes continuing a treatment can prolong the agony for a patient, and not even keep the patient alive.

"By not prolonging the agony . . . even though the intent is not for the patient to die, it is sometimes a consequence."