Washington (CNN) Julian Castro labeled the House Republican-led investigation into Hillary Clinton's emails a "witch hunt" and a "sideshow" from dealing with America's most pressing problems.

The Housing and Urban Development secretary accused GOP Rep. Trey Gowdy of "very intentionally trying to manipulate this witch hunt to play politics."

"That's unfortunate and it's one of the reasons Congress has a 19% approval rating," Castro told CNN's Jim Acosta Sunday on "State of the Union."

A trove of Clinton's emails from her time as secretary of state were released Friday by the State Department. A House panel investigating the attack on the U.S. embassy in Benghazi, Libya, led by Gowdy, has pushed for more State Department emails to be released.

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