London, UK - Former President Barack Obama slammed his successor Donald Trump's shocking claim that consuming Tylenol during pregnancy is linked to autism, saying it "undermines public health" in the US.

Obama warned of the Trump administration's "creeping authoritarian tendencies" as he addressed 14,000 people at London's O2 Arena.

"We have the spectacle of my successor in the Oval Office, making broad claims around certain drugs and autism that have been continuously disproved," the Democrat said, per Politico.

Trump on Monday tied autism to the use of Tylenol, a common brand of acetaminophen, and asked pregnant women to "tough it out" instead of taking the pain medication.

There is no causal link between taking acetaminophen during pregnancy and autism, and such claims have been widely condemned by both medical experts and autism advocacy groups.

Insisting that such messages can cause harm to pregnant women and parents of autistic children, Obama pointed out that autism is a wide spectrum, and that increases in diagnoses in recent decades are largely due to a "broadening of the criteria... so that people can actually get services and help."

"All of that is violence against the truth," he said, before warning that the US could be "backsliding towards that older way of thinking about the world."