Story highlights The Hatch Act prohibits employees in the executive branch, except the President, from engaging in political activity

Scavino's tweet called for GOP Rep. Justin Amash to be defeated in a primary

Washington (CNN) Senior White House aide Dan Scavino was reprimanded by the US Office of Special Counsel for violating the Hatch Act in a tweet, according to a letter posted by a Washington watchdog group.

The letter addressed to the Citizens for Responsibility and Ethics in Washington states that Scavino, the White House director of social media, violated the Hatch Act on April 1 when he sent a tweet calling for the defeat of GOP Rep. Justin Amash in a primary.

Big win for CREW! Dan Scavino reprimanded for Hatch Act violation! pic.twitter.com/noOXeUGOIk — Citizens for Ethics (@CREWcrew) June 9, 2017

The Hatch Act prohibits employees in the executive branch, except the President, Vice-President and some other high-level officials, from engaging in political activity.

In its letter to CREW, the Office of Special Counsel said that Scavino received a "warning letter" and "if in the future he engages in prohibited political activity while employed in a position covered by the Hatch Act, we will consider such activity to be a willful and knowing violation of the law."

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