The Greens will push for a parliamentary inquiry into the rise of obesity, especially in children, and whether a sugar tax on soft drinks is one way to combat the problem.
"We have a major health crisis on our hands with one-in-four Australian kids overweight or obese," leader Richard Di Natale said on Wednesday.
If the government doesn't act, the Greens will introduce a private bill for a sugar tax.
Liberal Democrat Senator David Leyonhjelm says instead of putting a tax on sugary drinks, there should be an impost on stupid authoritarian ideas.
"I think it would raise a large amount of money," he told reporters.
"There are a lot of stupid authoritarians around and they have a lot of stupid ideas and if we just tax them there would be no need to tax things like sugar."
The idea would also leave poor people alone, Senator Leyonhjelm said.
"This parliament seems determined to increase the cost of living to poor people."
The government flatly rejected the sugar tax push, labelling it a simplistic solution to a complex problem which would serve only to raise revenues.
"To cherry-pick one source of calories from all the abundance of food is not a logical response to a very complex problem," Assistant Minister for Rural Health David Gillespie told reporters.
