Commenting at a party fundraiser, Paul, R-Ky., said an Inspector General's report "makes it sound as if there was some sort of policy directive," the Boston Herald reported Tuesday.
"There's going to have to be an independent analysis of this, either an independent commission or something to look at this, because I think frankly people are losing their trust in their government," he added.
Paul said it was difficult to believe the White House was not aware of the targeting before the 2012 election.
"People within the IRS have known this for a year and a half," he said.
"Frankly I don't think there's anything more un-American than taking the power of the government and abusing your political opponents with it," Paul added. "I think that's why you're seeing such an outpouring against this."