Having lost the battle to skew the new Auckland council voting system to their advantage, the rich white business establishment is now turning its guns on MMP, the proportional voting system, which since 1993, has made Parliament a true House of Representatives.

Going along with it, seemingly with some reluctance, is Prime Minister John Key, saying he is honouring an election commitment made last year.

But given National has already broken its key election promise to hand out $4 billion in personal tax cuts over the next three years, it's a bit late to start pleading principle.

Once discarded, honour, like virginity, is rather hard to retrieve. Still, we Kiwis are pretty open-minded on such matters.

When Finance Minister Bill English jettisoned the promised tax cuts, National argued the betrayal was necessary for the greater good of the nation.

Most of us went along with this, knowing from experience not to believe everything we hear on the hustings. Indeed, the latest Roy Morgan poll suggests it's had no impact on National's standing, with the Government now nearly 12 per cent up on its election day support at 56.9 per cent.

If we can forgive him for taking cash out of our pockets, chances are Mr Key could quietly shelve the MMP referendum pledge alongside the tax cut promises, with impunity.

Governor-General Sir Anand Satyanand highlighted the representative nature of the current MMP Parliament at his Race Relations Day reception earlier this year.

To see New Zealand's growing diversity, "one only has to look at Parliament. Thirty-one of the 122 MPs, about a quarter, are of either Maori, Pacific or Asian descent and five are ministers".

He contrasted that with the situation 30 years ago when "just seven of the 92 MPs were of Maori descent, one of whom was a minister, and there were no MPs of Pacific or Asian ancestry at all."

He added that back then "all but four MPs ... were men to boot".

As Sir Anand acknowledged, MMP has made Parliament more diverse in many ways.

There are now 42 women MPs, making up 34 per cent of parliamentarians. There are openly gay members.

This diversity has come about in no small measure because parties, including both National and Labour, have placed "minority" representatives in winnable positions on their party lists.

Pansy Wong, a National list MP since 1996, became the first Asian electorate MP last year when she won the seat of Botany.

MMP has also, of course, brought diversity of ideas to the centres of power. The Greens, Act, the Maori Party all exist because of this electoral system, and our public life is better for the spread of views - however wacky some might seem.

Rod Donald, Pita Sharples, Margaret Wilson, Roger Douglas. Political debate would have been poorer for their absence.

Lobbyists for a return to the discredited First Past The Post voting system, like businessmen Peter Shirtcliffe and journalists such as Graeme Hunt and my colleague Fran O'Sullivan, who in a weekend column argued the old voting system "gave more power to the major party to implement sensible policies", seem blinded by nostalgia.

Have they forgotten the years of repressive state control under Nanny Muldoon? Or the unheralded Rogernomics upheavals that followed? The Muldoon-Lange years proved there's no guarantee that major parties, unfettered, will implement "sensible policies".

In The Hollow Men, the explosive exposure of the National Party based on party emails, Nicky Hager revealed that Mr Shirtcliffe was one of the chief puppet masters of the National leadership and the top donor in the run-up to the 2005 election campaign.

His donation was dependent on leader Bill English being dumped in favour of right-wing monetarist Don Brash.

Mr Shirtcliffe also masterminded the 1993 Campaign for Better Government, which spent around $1.5 million campaigning against MMP - and lost.

Like rust, he keeps gnawing away, personally affronted, it seems, that minorities should want a say in the running of their country.

Neither of the big parties wanted MMP, which is one of the reasons the rest of us voted for it. We'd lost confidence in the old two-party system. In both 1978 and 1981, Labour won more of the total vote, but National won a majority of seats and reigned supreme.

In 1981, protest against the system gained Social Credit 21 per cent of the total vote, but only two seats. In 1984, Bob Jones' New Zealand Party scored 12 per cent, but no seats. Then came the Rogernomics upheavals.

No wonder in the 1992 referendum, 85 per cent voted for a change to the electoral system and 70 per cent favoured MMP. As promised, it has made Parliament more representative.

Just as importantly, for those with a memory, it provided a way of controlling the unbridled power that went to the heads of people like Sir Robert Muldoon and Sir Roger Douglas.

As for swapping MMP for National's off-course substitute, Supplementary Vote (SV), that system is little better than straight FPTP. After the 1997 British election, a group of academics funded by the Economic and Social Research Council "replayed" the voting to compare what would have happened under competing electoral systems.

They then calculated how disproportional each system was, giving each a "deviation from proportionality" score. The lower the figure, the more proportional it was. MMP scored best on 2 per cent. FPTP, the system still used in Britain, had a DV score of 21 and SV, which some in National see as a compromise, was worse on 23.5 per cent.