A top-ranking House Republican on Tuesday accused the Department of Health and Human Services of "changing their story," after the Biden administration defended the legality of its reappointments for key National Institutes of Health officials that Republicans have questioned.

The claim from Rep. Cathy McMorris Rodgers, chair of the GOP-led House Energy and Commerce Committee, follows a Friday letter from the panel to HHS Secretary Xavier Becerra. 

The panel alleged that 14 top-ranking NIH officials were not lawfully reappointed at the end of 2021, potentially jeopardizing billions in grants they approved. 

It also raised concerns about affidavits Becerra signed earlier this year to retroactively ratify the appointments, in an effort the department said was only meant to bolster defenses against bad-faith legal attacks.

"Health and Human Services seems to keep changing their story. This is just their latest effort. I don't know if they don't know what the law is, or they are intentionally misleading," McMorris Rodgers told CBS News senior investigative correspondent Catherine Herridge on "America Decides" Tuesday.

In a statement to CBS News, an HHS spokesperson had criticized the panel's allegations as "clearly politically motivated" and said it stood "by the legitimacy of these NIH [Institutes and Centers] Directors' reappointments." 

"As their own report shows, the prior administration appointed at least five NIH IC officials under the process they now attack," the spokesperson had said. 

Asked about the Biden administration's response, McMorris Rodgers said that the previous reappointments were not relevant to the law the committee claims the Biden administration has broken. 

And she said that she thinks that the administration is responding to a provision that only governs pay scale, not propriety of the appointments themselves. 

"But what we are talking about is a separate provision in the law. It was included, it was added, in the 21st Century Cures to provide accountability to taxpayers and by Congress, it was intentional. And it is to ensure that these individuals actually are appointed or reappointed by the secretary every five years," McMorris Rodgers added. 

Democrats on the panel have criticized their Republican counterparts' claims as "based on flawed legal analysis," saying that the law is "absolutely clear" that "the authority to appoint or reappoint these positions sits with the Director of the National Institutes of Health, who acts on behalf of the Secretary of Health and Human Services."

"The shift in appointment power from the Secretary of HHS to the NIH Director in 21st Century Cures was actually a provision Committee Republicans insisted on including in the law during legislative negotiations in 2016," Rep. Frank Pallone, the committee's ranking member, said in a statement Tuesday.

CBS News reporter covering public health and the pandemic.