During a phone conversation on a commercial airplane late last week overheard by an NBC News reporter, the head of the Centers for Disease Control and Prevention slammed one of the White House's top Covid-19 advisers for providing President Donald Trump and the U.S. public with misleading information about the deadly pandemic.

"Everything he says is false," CDC Director Dr. Robert Redfield told a colleague while on a flight from Atlanta to Washington, D.C. on Friday, NBC News reported Monday morning. Redfield, a Trump appointee, later acknowledged to NBC that he was referring to Dr. Scott Atlas, a neuroradiologist with no expertise in infectious diseases or epidemiology.

Brought aboard the administration's Covid-19 task force in August after reportedly catching Trump's attention with his frequent appearances on Fox News, Atlas has been pushing the White House to adopt a so-called "herd immunity" approach to the coronavirus pandemic—a strategy public health experts warn would cause millions of additional deaths. Atlas has also publicly questioned the effectiveness of face coverings in preventing the spread of coronavirus.

"Since his addition to the task force, Atlas has become the medical expert who spends the most time with the president, and his profile has been elevated in recent weeks by his appearing in the White House briefing room when Trump speaks with reporters," NBC reported. "There is a concern among Redfield and others that Atlas continually briefs the president and misrepresents what other health experts have said in sworn testimony, according to a member of the task force."

As epidemiologist Eric Feigl-Ding noted on Twitter, Atlas "has been spreading misinformation for a long time," including by falsely stating that coronavirus poses "no risk" to children.

Despite Atlas' complete lack of experience in the field of infectious diseases, Trump has cited the radiologist in an effort to legitimize his false claims about the coronavirus.

"A lot of people do agree with me," Trump said during an ABC News town hall in defense of his insistence that the U.S. is "rounding the corner" on the pandemic. "You look at Scott Atlas, you look at some of the other doctors that are highly—from Stanford."

But in a letter about a week ahead of Trump's town hall, dozens of Atlas' former colleagues at Stanford University Medical School denounced the White House adviser for spreading "falsehoods and misrepresentations of the science" in a variety of areas, from mask use to his promotion of a herd immunity strategy.

"Many of his opinions and statements run counter to established science and, by doing so, undermine public-health authorities and the credible science that guides effective public health policy," the Stanford faculty members warned.