The state Opposition Leader, Mark McGowan, says he or one of his colleagues will introduce a euthanasia bill to parliament next year.

Mr McGowan says he is a supporter of voluntary euthanasia for people who are terminally ill.

He says a debate about euthanasia legislation is needed and when a bill is introduced, he would give his Labor colleagues a conscience vote.

"If someone else didn't do one, then I'd feel it incumbent on me as someone who has expressed my point of view, and as an elected member of parliament to do so," he said.

Mr McGowan later clarified his remarks.

"Any bill introduced by any member of the WA Labor Caucus, including myself, would be a private members bill and not a Labor or Government bill," he said.

He says Labor MPs would be free to vote as they wish on such a bill.