Rep. Justin Amash (Mich.) officially submitted his letter to leave the House Republican Conference on Monday, losing his committee assignment as a result.

“Today, I sent the attached letter to Republican leaders as formal notification that I am withdrawing my membership in the House Republican Conference and, consistent with House rules, resigning from the Committee on Oversight and Reform,” he tweeted.

In the letter addressed to House Minority Leader Kevin McCarthy (R-Calif.) and House Republican Conference Chair Liz Cheney (R-Wyo.), Amash wrote: Please accept this letter as formal notification that I am withdrawing my membership in the House Republican Conference, effective immediately, for the reasons outlined in my accompanying op-ed.

“Consistent with clause 5(b) of Rule X of the House of Representatives, I also am resigning from the Committee on Oversight and Government Reform.”