Ways and Means Committee Chairman Kevin Brady, R-Texas, became the latest GOP lawmaker to call for IRS Commissioner John Koskinen's head.

"Frankly, in my view, he's the most corrupt IRS commissioner that I've ever dealt with," Brady said on Monday. He "continues … to mislead Congress, and until he's removed, I don't think the IRS will ever regain its credibility.

"He certainly isn't making an effort for [improved] consumer service," Brady added.

"And it's one of the reasons why in our tax reform proposal we dramatically simplify the tax code. So we're proposing to bust up the IRS and redesign it into a 21 st Century [entity] focused on taxpayer service."

Koskinen survived an impeachment vote in the House last year but only because GOP leaders objected to the process that would remove him from office, rather than the notion that he should be fired.