Just as the smacking debate dogged the previous government, the fuss around folate has the potential to knock the gloss off this government if it doesn't act quickly.

The debate over whether to introduce folic acid into the nation's bread is a classic example of how government's lose their shine. It's one of those blindside issues that come from nowhere to muddy the political mood.

When the new National-ACT cabinet met late last year, I can't imagine anyone much remembered the deal Labour had made with the Australians to try to prevent neural defects in new babies. But then Labour never saw the foreshore and seabed ruling coming either. The folate debate won't become as big an issue – for one it's easier for National to put a lid on this – but in a similar way it will leave a lasting impression in the minds of many voters.

If National had been more vigilent and more experienced, they would have seen this coming. Instead, they left it late and now are in a politically untenable position. If you haven't got your head around this issue, let me give you a quick rundown.

New Zealand and Australia created a joint food standards authority back in 1991 (when National was in power) to harmonise food standards across both countries. During the previous Labour government, minister Annette King was convinced by lobbyists that introducing folic acid to a mass market product – bread, in this case – would improve the health of pregnant women and reduce the number of brain damaged babies born in both countries. Folic acid was, at that stage, seen as a wonder vitamin, good for all. Heck, the US has folic acid through much of its bread and its spina bifida rates have dropped significantly since the folate was introduced.

A number of critics say it would be cheaper and better targeted to simply hand out free folic acid pills to every pregnant woman. The problem with that argument is that for it to work most effectively, women need to be taking folic acid from about a month before they get pregnant, and given that at least half of the pregnancies in New Zealand are unplanned, well, you need to get it into women in some everyday product they'll be consuming whether they're pregnant or not.

And let's be very clear about this: Folic acid is very important for pregnant women, and in normal doses it's unquestionably very good for you.

Given the amount of minerals and vitamins being tossed into food these days and the fact folate is already added to a lot of cereals, King probably didn't expect much fuss.

She should have. The 'mass medication' label is both warranted and certain to wind up many Kiwis. What's more nanny state than forcing us to take our medicine whether we want to or not? This has got Mary Poppins written all over it. And not even the US puts it in every loaf of bread (except for organic loaves).

The argument against mandatory folate is strong, and getting stronger. For a start, it's using a sledgehammer to crack a walnut. While everyone gets the folate, it will save only an estimated three to 14 babies a year from neural defects. Of course if yours was one of those three babies (and it was Food Standards Australia New Zealand's own report in 2005 that estimated the benefit at three children per year), you'd be more than happy with the medication. But compulsion is a power all governments must be wary of using, and is that sufficient gain to justify such a big stick? If so, why not add half a disprin to all loaves to help older folk with heart problems? Where do we stop?

Another significant point is that New Zealand's spina bifida rate has been tracking down much like America's over the same period. I don't have any science to confirm this, but logic suggests that the increasing use of folic acid by pregnant women anyway, our improving diet (folate is naturally found in spinach, bananas, and avocados, amongst other foods), and its addition to cereals is making a difference without going the mandatory route.

But perhaps the most compelling argument is the handful of recent lab studies in the past year or so that suggest a link between "high levels" of folic acid and cancer risk. As a result, Ireland has put its planned introduction of folic acid to all bread on hold. While the expert panel employed there stressed that the studies were inconclusive, it added that new, better research was expected by the end of the year, so it would delay until it knew more.

The most serious risk, while still small, is for young boys and females in general. The New Zealand Food Safety Authority (which is different from the ANZFSA) has warned the government that 13.8 percent of males aged five to eight and 8.2 percent of females are going to exceed the upper level intake for folic acid. It would be terrible to learn in a decade or two that those heavy bread eaters had been put at a higher risk of cancer.

The Irish Food Safety Authority announced its decision to delay in March. Plenty of time, you would have thought, from National to have seen this coming. It was surely going to be asked, 'if Ireland's concerned enough to delay, shouldn't we be as well?'

The problem is our joint authority with Australia. A treaty was signed. National says they don't want the folate, but the law binds them. And it's true, we can hardly go around breaking treaties. And it's rather curious that the Greens – such champions of international law – seem to have so little regard for this document.

Having said that, I'd be very surprised if the Australians didn't see the virtue in delaying for a few months. I would have thought a few high level phone calls and some rational explanations would be enough to reach agreement without our neighbours sending the frigates over to put us in our place.

Instead, Food Safety minister Kate Wilkinson is changing positions by the day. Last week she was acknowledging the safety concerns but claiming that her hands had been tied by Labour's legacy. Now she's pointing to new research which says folic acid is safe at high levels after all.

She's panicking now, and it's not a good look. She was in an untenable situation last week, but at least it was rational, up to a point. She was right to say that the science on the folate-cancer link is "light". Jumping to the other side and saying that one new study suddenly makes everything alright simply makes her look as flaky as a croissant. If several studies showing a link last week were "light", one study challenging that is utter puff (pastry).

The political risk here is high for the government if they don't act quickly. At National's campaign launch last year, Bill English mocked Labour for responding to every issue with regulation saying,

"It will be a challenge to roll back the nanny state... but we will meet that challenge".

The hypocrisy cries have already begun. And the Bakers' Association and the powerful supermarket lobby aren't going to let up.

The only good news for National in all this is that Labour at least is as compromised by this issues as it is. Labour MPs can't lead the attack on the government when it was their policy. But voters don't need them to get their dander up.

If the government doesn't get out in front of this, it could eat away at it just as the smacking debate ate away at the previous government. The 'don't come into my home and tell me how to run my life' argument is identical (except that in this case it has more merit). And with the referendum coming up and National unlikely to want to reverse is position and amend the child discipline laws, its anti-nanny state credentials are in serious jeopadry.

John Key's in an double bind because he's a big fan of getting closer to Australia. But for his own political health he needs to get on the phone to Kevin Rudd pronto to get his government out of its untenable position.