Key Points:

John Key and Bill English ought to think very carefully before tampering with the New Zealand Superannuation Fund - even if the political risks of doing so may seem relatively slight at first glance.

The ever-deteriorating state of the Government's books has raised speculation National might temporarily halt contributions to what is more commonly known as the "Cullen fund".

The Prime Minister, however, says the matter has not been discussed at Cabinet level, while his Finance Minister likewise declares the Government's position has not changed and "we expect contributions to continue".

Their assurances do not sound totally convincing. It is inconceivable that such a moratorium - taxpayer-funded contributions to the scheme are currently around $2 billion a year - will not have been canvassed at some point, not least because the Treasury suggested a lower level of contribution in its November post-election briefing papers to English.

Since then, the fiscal horrors have only intensified. A short-term stop on contributions would avoid English having to borrow the money to fund the annual payment into the six-year-old fund. That would make it just a little easier for him to write a Budget which gets international credit rating agencies off his back. It might not be too difficult to convince people that it does not make much sense to borrow money to build up the fund - especially when world financial markets continue to nosedive.

Temporarily halting contributions for two or three years might also be saleable to the electorate as no one will actually be hit in the pocket by the potential consequences - at least not for a while.

There is one major proviso to such a course of action, however. The fund has one simple long-term objective - acting as a buffer to help future governments maintain existing state pension entitlements when the numbers reaching retirement age start to bulge and the superannuation bill correspondingly balloons.

The smaller the fund, the more difficult it will be to meet the shortfall in revenue necessary to maintain those entitlements. That will increase the pressure on governments to cut pensions or further raise the age of eligibility.

The question is whether dealing with short-term fiscal pressures now should override trying to solve a huge fiscal problem lurking in the future.

There are further reasons not to tinker with the contributions. The first is whether the Government will have the political wherewithal to restart them them once they have stopped. More important, however, is the (mostly) all-party consensus on superannuation policy. It took an age to reach. It will not take much to dissolve it.

National's cuts in KiwiSaver entitlements and its requirement that 40 per cent of the super fund be invested in New Zealand have already raised suspicions about its commitment to that consensus.

If contributions are to be halted temporarily, there must be buy-in from Labour as a minimum. It is in National's self-interest to get that. It will take the equity and housing markets years to recover.

Many people in their fifties already realise their retirement incomes are going to be severely squeezed without the added possibility of cuts in the basic pension.

Therein lies the major political risk for National - something Labour is wasting no time in seeking to exploit.