Now we were saying this last week and it hasn't gone away and it's not going to go away as the different parties announce their policies in the lead up to the election. How do we know what's true and what's not when it comes to costings?

When it comes to millions and billions of dollars, how do we keep tabs on it? We can't. Nicola Willis says there's an $18.2 billion gaping hole between Labour's promises, which are reinstating the pay equity scheme, billions, the future fund and the cap on public transport, and the money available to fund those policy promises.

Labour's finance spokesperson Barbara Edmonds says, Really? Willis should take a long hard look at her own accounts and explain the $56 billion hole in the roads of national significance." And so back round we go again.

As I mentioned last week, how are we to know when you've got Nicola Willis accusing the former CEO of Kāinga Ora of bidding $10 million more than the next commercial bid on a property back in the bad old days? He says that is an outright lie, it was $2 million more, which, you know, is $1.5 million too much. And then it turns out after, you know, a rule is put over the numbers, it was $8 million. So how are we to know?

I thought we had Treasury with a sharpened pencil doing the adding up to see if the promises can be paid for, and we kind of do, but I'm with economist Cameron Bagrie who told Early Edition this morning he's in favour of an independent fiscal institution.

Am I in favour of an independent watchdog to go through party political costings? I think that's a step too far. Am I in favour of what's called an independent fiscal institution which sort of sits aside the New Zealand Treasury, such as the Congressional Budget Office in the United States? The answer is yes. You know, I think we need to see a lot more sunlight, a lot more focus on the fiscal accounts, particularly issues such as population ageing and whether things such as New Zealand superannuation and exploding healthcare expenditure is going to be sustainable. Now, they will be sustainable, but the caveat is someone's going to have to pay. You know, the problem at the moment is that we tend to write out the cheques forgetting at some stage someone's going to have to pay and odds are it will be the younger generation down the track.

Well exactly, because the promises made today without the money to fund them are the bills the young people have to pay tomorrow and enough's enough, they've got quite enough on their plate.

It's a bit of a conundrum really because both National and Labour want to be calling the shots in the next government. They know that most voters are motivated by self interest, those that aren't tribal. They say, "You want my vote? Sure, what's in it for me?"

So the parties have to make promises even though they're constrained by the fact that we're in dire straits. And so we need to know that they are promises that can be kept for those of us that care and hopefully, hopefully there are more and more voters that do care.

Treasury can provide pre election policy costings but recognised political parties in Parliament are the ones who request the independent costings and analyses. It's not, you know, a public totting up as the policies come out. And rather than evaluating policies in a vacuum, Treasury and other relevant public service agencies assess the financial implications of the policies to ensure consistency and reliability.

But as a voter, I think we really need a body that can independently audit each party's promise as they go and see whether they're pie in the sky or doable. And it will only really be the main parties we need to worry about. Minor parties can make all sorts of outlandish promises and then say, Oh soz, the senior coalition partner put the kybosh on them. We really wanted every household in the country to have $1,000 per week but National Labour wouldn't let us do it, so sorry about that."

So it's only really National and Labour you need to have a long hard look at. But I would really like to see an independent authority with a head for figures do the sums and explain their workings in layman's terms so every voter will know what we're in for.

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