The comments come as New Zealand pushes for changes to the discriminatory rules of royal succession. Under the current law of primogeniture, male heirs accede to the throne before any older sisters.
Mr Key said today that New Zealand had been championing modernisation of the law, which would allow a first-born woman to accede to the throne.
"We've been putting on the record our case why we think that makes sense, why we think modernisation of those rules is important, and we are making it quite clear to anyone who'll listen we think this is an important step," he said today.
Asked if New Zealand was leading the way, Mr Key said he was "not uncomfortable with that description".
"My belief is that's a cause New Zealand should continue to champion, so we are a strong voice in that debate and if there's change I think that will be change for the positive."
Mr Key said he was opposed to gender discrimination.
"I think in this area New Zealand's got a great track record and true credentials, and it's my view that we can lend our voice in this area and actually make positive change," he said.
"As far as I'm concerned, and I think the majority of New Zealanders would agree with me, we judge people on them as individuals and their ability and their values, not on their gender."
Mr Key said he was also supportive of changes to allow non-Anglicans to accede to the throne.
The British monarch is head of state of 16 Commonwealth nations and any change to the line of succession would require legislation in all those countries.
The current heir to the throne is Prince Charles, who Mr Key said he was "super impressed with" when he met him before the royal wedding.
"He was, I thought, very in touch with issues around the world, he was extremely personable and the reality is that there's automatic succession anyway, at the point that the Queen passes away, to Prince Charles.
"I think he'd make a fine king and from that perspective we look forward to welcoming him to New Zealand some time in the future, hopefully he'll come and visit us."
Mr Goff said he would not personally comment on the suitability of individual heirs like Prince Charles.
"I'm sure he'd do his very best," he said.
Mr Goff added he had "enormous respect" for the Queen.
"I think as long as she's alive she will be Queen of New Zealand. At the point that she is no longer queen, New Zealanders will probably want to think about what they do for the future.
"But that's a decision for New Zealanders, it's not a decision for individual politicians -- it's a decision that all of us will need to make about what our future head of state might look like."
Mr Goff said the monarchy was very popular at the moment and if the issue went to a referendum New Zealanders would likely retain it.
"But as time passes, attitudes change and one day New Zealand will want to repatriate the head of state position to a New Zealander."
