New Zealand's constitutional arrangements and the issue of becoming a republic will soon be on the political agenda. Here's why - and why it's dangerous.

There's almost a consensus between the parties on Australia becoming a republic. It will be a good diversion for New Zealand politicians, ironically not in a fit of homegrown nationalism, but meekly following an Australian fashion and proving the opposite of independence. And a dependence on others' moods.

The only New Zealand politician of substance who has spoken up for a republic was Jim Bolger, who did so after it became an issue in Australia - and a few weeks after a visit by Australian republican Prime Minister Paul Keating.

It was natural that most newly independent countries asserted their independence by declaring themselves free of imperial foreign crowns. New Zealand, Australia and Canada were different.

We did not, except for some indigenous people, see the British system as tyrannical. We were colonised later than most places and we sought the rights of Englishmen and all that British democracy and common law had evolved into.

The Crown was seen as the protector of Maori rights and we still speak of settlements as being between the Crown and Maori. Curiously, it took our Parliament until 1947 to finally ratify the Statute of Westminster passed by the British in 1931 granting us complete independence.

This important step was not celebrated as some historic act of separation or independence, just a natural evolution.

Why could further change be dangerous? Because it is most likely to be done in a fit of populism and will represent ad hoc change.

Governments have the right to introduce GST or not, nationalise or privatise. But issues of constitutional consequence, once made, are difficult to unmake.

We abolished our rights of appeal to the Privy Council without much debate. We rejected first-past-the-post in a public fit of disgust because politicians seemed out of control.

The promise of another referendum on the future of MMP has not eventuated. A few politicians want to abolish the Maori seats and the Treaty of Waitangi. Others want the Treaty to be our constitution.

It's not good enough to pass laws saying the law should take into account the principles of the treaty without defining what they are. The treaty is vital - if we didn't have one we would have to invent it.