The five-year term of the Government has been marked by profound and often deeply controversial changes to our social order.
Civil unions will soon be a feature of society. Prostitution has been legalised. The Property Relationships Amendment Act, in effect, deemed those in de facto relationships to be married.
Smoking has been banned in restaurants, clubs and bars. Access to the Privy Council, as the highest court, has been abolished and a new Supreme Court established in its place. And the signal that the abolition of the monarchy, in favour of a republic, is next on the agenda is unmistakable.
These changes were, and are, opposed by substantial minorities - in some cases, possibly the majority - of New Zealanders. And the experience has left many harbouring serious doubts both about the way in which we elect our Parliament, and the way in which we make major changes to our key institutions.
They ask, correctly, whether MMP has delivered on the promise of a more consensual, more accountable form of government. And they ask how it is that a Parliament of 120 representatives can impose such profound changes on our social institutions without seeking a specific mandate from the public.
Even supporters of some of these changes have been disquieted by the spectacle of so-called conscience votes being managed by the ninth floor of the Beehive, down to the last abstention.
That the advent of MMP has resulted in greater representation for women and ethnic and other minorities is beyond doubt. Whether it has produced the more accountable, more consultative style of Government promised by its advocates is open to the most serious challenge.
Indeed, it is arguable that the reliance on backroom deal-making with minor parties to make progress with legislation has removed the whole process one step further from direct accountability to the public, the more so when some of the key participants are able to enjoy the comparative shelter of election as list MPs.
There is a widespread impression among New Zealanders that when MMP was introduced we were promised an opportunity to review the position by way of referendum two elections hence. The fact that this review was undertaken by a select committee of MPs, without any public referendum whatsoever, is rightly seen as self-interest on steroids.
The time has come to put the matter to the test by way of a new referendum on the manner by which we elect our MPs, inside the next term of office. That is a proposition I will ask the National Party to endorse as a matter of policy.
Any referendum need not be restricted to two choices. It may be, for example, that in addition to the former first-past-the-post system and the MMP system, New Zealanders will want to consider the supplementary member (SM) system, which would cut the number of list MPs by half. That would provide some assurance of retaining improved ethnic and gender balance (arguably the only benefit of MMP) while delivering a more accountable Parliament.
A great benefit of both the first-past-the-post or SM systems is that they would make possible a substantial reduction in the size of Parliament, to 100 MPs or even fewer, with a consequent reduction in the size of the Executive. Reductions to both would be very desirable.
If a referendum is the appropriate means to resolve such important constitutional issues - and I can scarcely imagine a less appropriate process than a select committee made up of people with a very direct personal interest in the decision, as with the review of MMP - why should we restrict such an approach to the electoral system? Why not use referendums more widely to determine other changes that significantly affect our social landscape?
I am mindful of the famous comment of the great British parliamentarian of the 18th century, Edmund Burke, that "your representative owes you not his industry only but his judgment, and he betrays, instead of serving, you if he sacrifices it to your opinion". But it has been with a growing sense of discomfort that I have seen controversial social legislation being managed through the Parliament by the Government.
It is not simply that I disagree with some of the measures it has promoted. What troubles me is that, unlike many other measures it has introduced, it can claim no specific or even implied mandate for these changes.
The legalisation of prostitution and the institutionalising of civil unions are not matters on which the Government or, indeed, any political party campaigned at the last election. It sought no mandate on such matters, and it has none. Yet far-reaching changes have been made, leaving distraught and angry minorities, possibly majorities, in their wake.
Far better, I suggest, in the absence of a mandate won at election time, that such controversial changes should at least enjoy the legitimacy of endorsement by a referendum of all people of voting age.
No doubt election-year caution will see such controversial social measures given a wide berth for the short term. Indeed, the Prime Minister was quite open in her cynicism in this respect as the civil union legislation was passed under urgency before Christmas.
The determination of the Government to advance its social agenda has left deep scars and even deeper doubts about the way we elect our MPs, and the extent to which those MPs owe true accountability to the public.
It is timely, then, to consider greater use of referendums to resolve those controversial social issues for which the Government and the Parliament can legitimately claim no mandate.
And even more so to provide the public with the opportunity to pronounce judgment on the MMP electoral system, which they have thus far been denied.
* Don Brash is leader of the National Party.