Duncan Garner has lashed out at the Government, accusing the $5.5 billion surplus of being an election bribe.
The 2017/18 financial books were opened on Tuesday and a major tax haul of $80.2 billion has left the Government flush with money.
Rainy day means effectively election bribes.
It's so much Finance Minister Grant Robertson has said he won't be ruling out tax cuts.
But The AM Show host Duncan Garner said it's now "party time" for the Government and the money is earmarked for one thing, ensuring Labour can secure a second term at the 2020 election.
"Rainy day means effectively election bribes. It means things like student allowances, you watch this, even tax cuts are now being considered," he said.
"For Labour, I mean, that's the equivalent of swearing, that's the equivalent of swallowing a dead rat whole.
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"This is about snookering National, giving them no room to move, pinch a few of their voters in the middle, send a note to their leader - 'We won, you lost,' that's what they'll say."
Garner said the Government only had the money from collecting excess tax, money New Zealanders should be seeing spent.
"It is your money, it is your money, now imagine a law that said that had to be returned to us immediately if they couldn't find a way to spend it, they'd find a way to spend it alright wouldn't they," he said.
"In fact this Government's problem is what to do with it, how's this, a billion dollars of the $80 billion they took in our tax last year that was meant to be spent on some half-baked idea that never came to fruition.
"They've kept this for a rainy day, they just kept all this money on the side."
Watch the full commentary above.
The AM Show with Duncan Garner, Amanda Gillies and Mark Richardson, weekdays 6-9am on RadioLIVE and streaming live to the rova app on Android and iPhone.