Conservative radio host Glenn Beck says that it's "reasonable" to investigate whether President Barack Obama's nominee for CIA director converted to Islam because the theory is "plausible."

Last week, former FBI agent John Guandolo, who resigned after engaging in a sexual relationship with a witness, told radio host Tom Trento that John Brennan "did convert to Islam when he served in an official capacity on the behalf of the United States in Saudi Arabia."

"His conversion to Islam was the culmination of a counterintelligence operation against him to recruit him," Guandolo asserted. "The fact that foreign intelligence service operatives recruited Mr. Brennan when he was in a very sensitive and senior U.S. government position in a foreign country means that he either a traitor … [or] he has the inability to discern and understand how to walk in those kinds of environments, which makes him completely unfit to the be the director of Central Intelligence."

Guandolo later repeated his accusations during an interview with Beck's website, The Blaze.

"These accusations are very serious, and such accusations demand serious consideration of all factors involved," The Blaze's Mytheos Holt wrote, adding that the allegations were "impossible to prove or disprove, except to take Guandolo’s word on it, since his sources are anonymous."

On Wednesday, Beck told viewers of his webcast that he agreed with Holt.

"I will tell you, I don't know if this is true or not," Beck admitted. "I will tell you that there is so much in John Brennan's background that should be questioned that this is plausible."

"Now, if somebody makes a charge like that, shouldn't we at least explore it before we put him as the chief of all intelligence?" he asked. "It seems that we can't ask reasonable questions any more."

Watch this video from The Blaze, broadcast Feb. 13, 2013.

(h/t: Right Wing Watch)