The New York Times, citing senior US officials, first reported that Comey believes Trump's unsubstantiated claim about his predecessor to be false. The department has not made any statement.
Comey made the request on Saturday because "there is no evidence to support it, and it insinuates that the FBI broke the law," the paper reported the officials as saying.
Neither the FBI nor the Justice Department immediately responded to an AFP request for comment.
Questioning the president's truthfulness, Comey's extraordinary measure provides an indication of the implications of the uncharted territory Trump has entered with his accusation.
However, although the Justice Department -- which is headed by Trump's staunch supporter Attorney General Jeff Sessions -- oversees the FBI, it is not clear why Comey didn't issue a statement himself.
Trump made his claim in a tweet on Saturday.
"How low has President Obama gone to tap my phones during the very sacred election process," he wrote. "This is Nixon/Watergate. Bad (or sick) guy!" He provided no evidence to back up the claim.
Obama denied the allegation via a spokesman as "simply false."
However, the Republican chair of the House Permanent Select Committee on Intelligence, Devin Nunes, said his panel would look into Trump's claim after the White House on Sunday urged Congress to investigate his allegation.
The accusation has prompted a firestorm of criticism, with many saying Trump's incendiary claim was aimed at diverting attention from a series of revelations about his aides' meetings with Russian officials.
grf/mdl
source: news.abs-cbn.com
