Former CBS News anchor Dan Rather says President Trump's administration is "in freefall" less than two months after the inauguration.

"The sheer level of paranoia that is radiating out of the White House is untenable to the workings of a republic," he wrote on Facebook Monday.

"I have a real question if President Trump actually believes what he is saying," Rather added. "Even [former President] Richard Nixon, the most paranoid president to date, ruled for years with a relatively calm hand."

"This Administration has been an off kilter whirlwind since the inauguration, and news reports suggest that seething anger from Mr. Trump is only getting worse."

Rather said public figures are responsible for challenging Trump after he recently claimed former President Barack Obama wiretapped him last year.

"The man who sends out a twitter tirade accusing a former President of crimes for which he provides no evidence, the man who doubles down when anyone with any sense pushes back, that man is our Commander in Chief," he said.

"Every one who normalizes Mr. Trump now, or has in the past, will have to answer to future generations for their acquiescence, silence or sophistry - if, indeed, not outright cowardice," the former "CBS Evening News" anchor added.

"Conspiracy theories are corrosive in society at large. When they dictate national policy, they can be lethal."

Rather added that Trump's allegations against Obama will not distract Americans skeptical of his ties with Russia.

"As the questions mount around Russia, as the circles of defense begin to falter, the determination to create diversions will escalate. [But] we have woken. We are paying attention. And we love our country too much to let it falter without a fight."

Trump claimed on Twitter last Saturday that Obama had his "wires tapped" in Trump Tower before Election Day last year, without offering any evidence.

Kevin Lewis, a spokesman for Obama, said last Saturday that Trump's claims about his predecessor are "simply false."

Administration officials have since stood by Trump's accusations, pressuring Congress to find proof.