Sen. Marco Rubio (R-Fla.) speaks in Washington on June 13. (Charles Dharapak/AP) Sen. Marco Rubio (R-Fla.) speaks in Washington on June 13. (Charles Dharapak/AP)

Sen. Marco Rubio (R-Fla.) sent a letter Monday to Health and Human Services Secretary Kathleen Sebelius questioning why the agency was spending at least $8.7 million to promote the Affordable Care Act through television ads.

Calling it a "blatant misuse of federal dollars to promote a fundamentally flawed law," Rubio suggested the Centers for Medicare & Medicaid Services should abandon its plan to launch an advertising blitz about the law as the open enrollment date of Oct. 1 draws near.

"Until critical questions can be answered regarding the availability and type of health insurance to be provided by ObamaCare, it is unconscionable to spend taxpayer dollars to promote and advertise ObamaCare plans that have yet to be finalized," he wrote. "While the Administration should be abandoning this disastrous law, instead it is imprudently and blindly promoting poor policies that will harm Americans and American businesses, and misappropriating public funds in an effort to sell bad ideas to good people."

HHS spokeswoman Joanne Peters, who would not confirm the size of the ad buy, defended the administration's decision to spend money on the issue. “Starting Oct. 1, millions of Americans will be able to access quality, affordable health coverage for the first time, and we will continue educating and informing the uninsured of this opportunity,” she wrote in an e-mail.

HHS regularly runs ads at the start of Medicare enrollment in the fall, according to an agency official, and is now doing the same for the opening of state and federal insurance marketplaces. The bulk of advertising spending on Obamacare is expected to come from insurers, who plan to spend hundreds of millions in an effort to enroll new customers, as well as by opponents of the law.

Rubio learned about the size of the buy from a media buyer the senator's campaign has worked with in the past, according to his spokesman Alex Conant, adding that since Rubio has sent the letter the ad buyer has seen another $2 million in reserved ad time. Conant added the senator and his staff will  "do whatever we can to stop taxpayer dollars being used in this way."

Republicans have continued to criticize the health-care law and push for its repeal as it approaches a critical stage in its implementation, though these attacks have receded in recent days as most lawmakers have turned their attention to the prospect of a military strike against Syria.