The Australian Medical Association has called for a tax on sugary drinks to tackle obesity and for water to be the “default beverage option” with meals.

In a position paper, released on Sunday, the AMA backed a number of measures to decrease obesity including banning junk food ads targeted at children.

Although the AMA labelled a tax on sugar-sweetened beverages “a matter of priority” in September, the prime minister, Malcolm Turnbull, rejected the idea of a 20% tax on the grounds that consumers already paid “enough taxes” at the supermarket.

The paper argues that although many Australians have access to high quality fresh foods “most do not consume these in the recommended amounts”.

One-third of food intake comes from highly processed junk foods and beverages and half of Australian adults have a body weight that puts their health at risk, it said.

The paper notes that flavoured waters, sports drinks and fruit juices “contain significant quantities of added sugars”. Energy drinks also contain large quantities of caffeine and “should not be readily available to those aged under 18 years”, the AMA said.

On Sunday the Coalition insisted it was taking the required action to tackle the challenge of obesity and would not make a deal that taxes sugary beverages.

“We do not support a new tax on sugar to address this issue,” a spokesman for the health minister, Greg Hunt, said. “Unlike the Labor party, we don’t believe increasing the family grocery bill at the supermarket is the answer to this challenge.”

In September Turnbull questioned the scope of a proposed sugar tax, noting that: “There is a lot of sugar in a bottle of orange juice … Are you going to put a tax on that?”

Turnbull suggested better labelling and understanding of “the health message” such as to “get up and walk” would solve obesity.

The AMA also called for increased nutrition education and food literacy programs.

“Advertising and marketing unhealthy food and drink to children should be prohibited altogether, and the loophole that allows children to be exposed to junk food and alcohol advertising during coverage of sporting events must be closed,” the president of the AMA, Michael Gannon, said in a statement on Sunday.

Water should be the default beverage option in all instances where a beverage is provided with a meal, the AMA paper said.

The AMA recommends the federal government continue food fortification programs by requiring manufacturers to add certain vitamins and minerals to foods or specific ingredients.

The push for a sugar tax has been led by the Obesity Policy Coalition. Its executive manager, Jane Martin, said obesity cost Australia an estimated $8.6bn in 2011-12 in direct and indirect costs such as GP services, hospital care, and absenteeism.

Researchers have suggested a tax on sugary drink combined with a subsidy on fruits and vegetables could save the health sector $3.4bn.

The AMA statement notes that 22% of Aboriginal and Torres Strait Islander people live in households that have run out of food and not been able to purchase more at some point in the past 12 months. It said that nutrition and food security were important aspects of the Closing the Gap initiatives.

In 2017 the ninth Closing the Gap report found the overall mortality gap between Indigenous and non-Indigenous Australians was widening.

Outback stores should “prioritise and facilitate access to affordable nutritious foods”, the AMA said.

The AMA said that state and local governments should identify “food deserts” and work with developers to ensure access to fresh foods is improved.