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 tapp 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.