Former Revenue Minister Peter Dunne calls rumoured Labour tax policy 'far too complex'

When is a fruit or vegetable tax-free under Labour's rumoured election tax policy? 

Does it have to be fresh? Could it be canned? What about frozen? Here's a spanner: dried fruit? 

The supermarket is a place where we all spend a lot of our money. A large chunk of that is for food from the produce section.

This is where National claims Labour is rumoured to be removing GST.

If National's finance spokesperson Nicola Willis is right, there'd be no GST on things like pineapple, mango, green beans, and beetroot. 

But there's a problem. 

"What about canned fruit?" asks former Revenue Minister Peter Dunne. "What about fruit juices or derivatives? The same with vegetable products. Where do you draw the line?"

It's a good point because elsewhere in the aisle lurks this can of worms in the form of canned beetroot, canned beans, canned mango and canned pineapple.

The frozen section adds more brain freeze: frozen mango, and frozen green beans. 

And pick your spanner from the pick-n-mix: there's dried mango and pineapple too. 

"It's far too complex to even make workable," said Dunne. 

Dunne spent more than eight years as Revenue Minister and many proposals for policies like this came across his desk - but none were workable. 

Finance Minister Grant Robertson knows that too: 

"It becomes an absolute boondoggle to get through," he said last year. "If you do it off fresh fruit and veges or even staple products, then you get into an argument, what's the difference between beetroot and canned beetroot."

A can of Watties beetroot is $3.19, much cheaper than three fresh beetroot which cost $4.80. So which one would be GST-free?

"We're not going to play the rule-in, rule-out game," said Deputy Prime Minister Carmel Sepuloni. "The only things we have said publicly that we have ruled out are a wealth and capital gains tax."

It's been Labour's policy before. The then-leader Phil Goff announced it ahead of the 2011 election. It was axed two years later. 

But could it be different this time? 

"I think the intention is clear and that's often true in most cases but the problem is we get unintended consequences and we get, as the Tax Working Group called it, complex and arbitrary boundaries," said economist Stephen Hickson.

It's certainly complex for the back-to-basics Government which has now added fruit and vegetables to its bread-and-butter agenda.