Washington DC - Dr. Peter Marks, a former top US vaccine official, has criticized Health and Human Services (HHS) Secretary Robert F. Kennedy Jr. for promising to reveal the source of autism by the end of this year.

Marks recently sat down for an interview with the CBS News show Face the Nation, during which he said autism was "an incredibly complicated issue" that couldn't be solved in such a short period of time.

"If you just ask me, as a scientist, is it possible to get the answer that quickly? I don't see any possible way," Marks argued.

His remarks came after Kennedy, a well-known vaccine skeptic, announced last week that his department would be launching a "testing and research effort" to discover the causes of autism by September and "eliminate those exposures."

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Marks accused the politician of "giving people false hope" and said he would not accept the results being "an environmental toxin" such as vaccines, as Kennedy has repeatedly suggested, because "we've studied them in so many millions of children."

Since 2016, Marks had served as the top vaccine scientist in the Food and Drug Administration.

But Marks resigned earlier this month, leaving behind a letter that argued Kennedy doesn't value "truth and transparency," but "rather he wishes subservient confirmation of his misinformation and lies."