Act Leader David Seymour said the Government is clearly preparing to introduce a sugar tax despite previously ruling it out this term.
OIA documents reveal that the Ministry of Health is looking into a sugar tax.
Health Minister David Clark said the ministry chose to prepare a document, which explored the feasibility of a sugar tax, to provide him with a range of potential interventions to help tackle obesity.
This follows the Government ruling out any possibility of a sugar tax for the time being.
David Seymour told Kate Hawkesby the Government is clearly preparing to implement a sugar tax.
"I put in some request under the Offical Information Act and it turns out, frantically beavering away are all these public health types who are very much preparing the ground for a sugar tax."
However, David Clark says he is still reviewing the report and they have ruled out a sugar tax this term.
Seymour said if they aren't planning on introducing the policy, then they are wasting money.
"You would hope they aren't preparing policy just for fun and just to keep researchers employed, doing things that they have no intention of implementing."
"So if they have no intention of every doping this then they are wasting a whole lot of money and time."
The document says areas for future work could include taxes, levies and prices, "eg. sugar-sweetened beverage tax or minimum pricing".
Other areas include:
• Reduced portion sizes from manufacturers, restaurants and in retail
• Restricting access of processed foods around or near schools and workplaces
• The reformulation of processed foods
• Looking into advertising, marketing and price promotions
• Mandatory Health ratings and sugar labelling
David Seymour said a sugar tax would punish the majority of New Zealanders, who were responsible people, for the sins of an "irresponsible minority".
"It's not a good policy. Rather than being free people served by the Government, we are kind of here to be poked and prodded and taxed and harangued into behaving the way the Government would like according to its wellbeing budget and general budget."
He said it's not fair to treat all New Zealanders "like idiots" just because "some idiot feeds their kid Coca Cola in a sippy bottle".
"All of us get treated like idiots who aren't allowed to consume and enjoy the things that we want."
Seymour said a tax won't help people who are clearly acting "irrationally".
"Infants who have to have the rotting stumps of their teeth removed under general anesthetic by dental surgeons, their parents are acting irrationally, more labels, more taxes aren't going to help."
"It's not your first or second coke that makes you obese, it's your ninth or your tenth."
"The problem with a sugar tax is that all of us who have one or two are going to pay the tax, but the effect of your ninth and tenth well that's taxed at the same rate."
However, New Zealand Dental Association president, Dr Bill O'Connor told Mike Hosking he is all for a sugar tax.
"We are very supportive of a sugar tax but not surprised that the Minister is not following through with it at the moment because he's been signalling that he's not going to."
He said international evidence shows that sugar taxes work.
"The evidence so far shows that in countries where they have introduced sugar taxes it is working."
"It's just one of many tools that you can use to reduce the sugar intake of your population and anything that does that is beneficial."