Charles would give it his best shot - Goff

A day after Prime Minister John Key revealed he is a monarchist who is "super impressed" with Prince Charles, Labour leader Phil Goff could only muster a half-hearted compliment for the potential future king.

"I'm sure he'd do his very best," Mr Goff said.

He did not want to make personal comments about the "qualities of individuals like Prince Charles" but had no problem saying he had "enormous respect for Her Majesty the Queen".

"I think as long as she's alive she will be the 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.

"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."

This week Mr Key said he supported New Zealand remaining a monarchy because of historical and cultural ties to Britain.

He said Prince Charles would make a fine king and although New Zealand would eventually become a republic, it would not happen "under my watch".

Meanwhile Mr Key confirmed that New Zealand was pressing other Commonwealth countries to change the discriminatory law on royal succession.

Currently the eldest son has the first right to the throne, even if he has elder sisters, and a female can only accede to the throne if there are no direct male heirs. The law also bans Catholics or anyone married to a Catholic from ascending to the throne.

New Zealand has been pushing for a change to 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," Mr Key said.

Asked if New Zealand was leading the way, Mr Key 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.

"We judge people as individuals and their ability and their values, not on their gender."

Mr Key also supported changes to allow non-Anglicans to accede to the throne.

Green MP Keith Locke said if the succession law was going to be changed, gender and religion discrimination should be dealt with together in one blow.