Food stamp participation is at an all-time high, costing taxpayers $80 billion in 2012 alone, but the U.S. Department of Agriculture refuses to make public how much of that money pays for junk food.

A 2012 Yale study estimated Supplemental Nutritional Assistance Program benefits, formerly called food stamps, pay for $2 billion in sugary drinks alone every year. A 2010 study by the Center for Science in the Public Interest said that spending was even higher, estimating soda companies reap as much as $4 billion each year in SNAP money.

SNAP benefits are legally allowed to pay for everything from ice cream to soda. But because the USDA doesn’t make food stamp purchase data public, it’s difficult to know how much that junk food costs taxpayers.

Rep. Tom Marino, R-PA, introduced the SNAP Transparency Act on Friday, which would require the USDA to publicize what food stamps pay for.

“SNAP is a perfect example of how our government spends too much money with too little oversight and accountability,” said Marino in a statement.

Not only should people know how their tax dollars are being spent, but food stamps shouldn’t pay for junk food at all, the National Center for Public Policy Research said Friday. The group was a vocal opponent of New York City’s soda ban, but strongly supports Marino’s SNAP Transparency Act.

“The National Center and I have been a vocal proponent of Coca-Cola’s right to sell any and all of its products when it comes to the nanny-state restrictions of New York Mayor Michael Bloomberg and his ilk, but it’s with the understanding that sugary beverages are a specialty item,” said David Almasi, the National Center’s executive director. “When it comes to public assistance, I want people buying what they need with my money and not what they desire.”

A coalition of more than 16,000 health care journalists and government watchdogs wrote to Agriculture Secretary Tom Vilsak earlier this month asking him to make SNAP information public.

“The USDA does not disclose which products are purchased with SNAP dollars – or how much is spent on each product, in aggregate – information that is extremely relevant to the public-policy debate about causes and health consequences of obesity, particularly in children,” they wrote. Companies that make soda and other junk food oppose changing SNAP rules to restrict purchases to “healthy” foods, saying nutrition-based rules are arbitrary and can open the door to further restrictions. “We join with others in the non-alcoholic beverage industry and the broader food products industry concerned about any static policy, including SNAP benefits, that would look across 300,000+ items in a grocery store and arbitrarily restrict the sale of some of our products based on calorie content,” a Coca Cola official said in response to questions from the National Center.