"I'm sorry to say that this administration just doesn't seem to get it. You just don't seem to get it," Harkin told Health and Human Services (HHS) Secretary Kathleen Sebelius in a hearing.
"We just keep thinking about how we pay today's bills. If that's all we're going to do, we're looking at the next 30-40 years going after the same chronic diseases we've had in the last 40-50 years."
Harkin leads the Senate Health, Education, Labor and Pensions Committee and is a fierce advocate of preventive medicine — the idea that healthcare should seek to prevent illness rather than merely treat it.
He spoke last year of an "ironclad agreement" with the White House not to take more prevention dollars. The payroll tax cut extension of February 2012 had cut $5 billion from the ObamaCare fund.
Sebelius appeared Wednesday before the Appropriations subcommittee on Labor-HHS, which Harkin also leads.
She defended the choice to use prevention dollars to educate consumers about their benefits, which include preventive benefits, under the Affordable Care Act.
"We are focusing an enormous amount on reaching people and connecting them, not with a one-time program or effort, but with ongoing healthcare," she said.
"There's no question that this budget represents some very difficult decisions," Sebelius added.
"Our outreach and education are [ensuring that] in the most underserved communities, they have access to the preventive benefits that are now, by law, part of insurance coverage."
Republicans have called the Prevention and Public Health Fund an "unaccountable slush fund" and criticized its investments.
They respond to Democratic criticism by pointing to Obama's recent budgets, which propose to cut the fund.
The debate made headlines elsewhere on Capitol Hill Wednesday as the House prepared to consider a bill that would shore up ObamaCare's short-term insurance program with prevention dollars.
"The administration is using the 'Prevention' fund as a mass marketing and financing machine for ObamaCare," Rep. Joe Pitts (R-Pa.), the bill's sponsor, wrote in The Hill.
"The level of spending has been outrageous with hundreds of millions of dollars spent on some very questionable programs, and the rampant spending continues."