Treasury's opening the Government's books exercise is a bit like closing the stable door after the horse has bolted.

It assumes that politicians will look at the figures and tailor their election promises accordingly.

In reality it gives them wriggle room to get out of something they've floated publicly.

In fairness to Jacinda Ardern, she didn't raise the prospect of hiking the top tax rate, the media did.

But she didn't deny it was part of her plans saying she'd wait to see the state of the books and make a decision then, adding it'd probably take several days to crunch the numbers.

Well the numbers were crunched within just a few hours and the top tax rate won't be changed.

If she doesn't realise that raising taxes does not a Government make, then she'd do well to look at the three previous elections she's been involved in with Labour, especially the last one.

David I'm-ashamed-of-being-a-man Cunliffe was at the helm and made such a botch of remembering details about the capital gains tax proposal that he himself devised, during a television debate with John Key, that it ran Labour off the fiscal rails.

Tax is again shaping up to possibly be Labour's Achilles' heel and simply sidelining the issue to a taxation working group after the election won't do.

Ardern was asked the other day whether finance was her weak point and she replied with a curt, "no".

Being up against the former Finance Minister and one time Treasury wonk Bill English, she'd do well to know her stuff in what is a political minefield. Perhaps that's why she'll spend much of today with the spin merchants schooling her up on the difference between a hedge fund and the fence that her mum's offered to paint to make her house look presentable in the lead up to the election.

And while we're about sprucing things up, it's time Winston Peters had a word to the man he's put in charge of state owned companies.

Labour and the Greens have had the good sense to back away from the idea of renationalising the energy sector but it seems Richard Prosser's caught in a time warp, warning a room full of suits in Wellington to get rid of their Contact Energy shares right now.

Blood clearly pulsating to his head, Prosser told them not to expect the current market value for their shares, they'll be purchased at whatever they were bought for, and no more.

That saw Act's David Seymour having a lipstick on a pig moment, telling the audience Prosser's a f***ing idiot but unlike Gareth Morgan with Labour, he was most definitely referring to the man and to New Zealand First as well.

Not unlike Morgan, it got Seymour the publicity that he's so desperately been craving.