House Speaker Nancy Pelosi on Thursday named Wyoming Republican Liz Cheney to her newly formed select committee to investigate the Jan. 6 Capitol attack, making her the lone GOP appointee among Pelosi's eight picks.

"We're very honored and proud that she has agreed to serve on the committee," Pelosi said Thursday in announcing Cheney's appointment. 

Cheney, already ousted from GOP House leadership for routinely blaming former President Trump for sparking the attack, joined with all Democrats Wednesday to vote in favor of forming the committee along with Rep. Adam Kinzinger, R-Ill. 

CAPITOL RIOT: HOUSE CREATES COMMITTEE TO INVESTIGATE JAN. 6 ATTACK

Cheney said the committee is the only option remaining to thoroughly investigate the "unprecedented assault on Congress." Republican leadership has dismissed the committee as partisan, and GOP Leader Kevin McCarthy reportedly threatened to strip Republicans of their committee assignments if they accepted an invitation by Pelosi to join the panel. 

Undeterred, Cheney said she's "honored" to serve on the committee, and her oath to the constitution and commitment to rule of law and peaceful transfer of power "must always be above partisan politics."   

Rep. Liz Cheney, R-Wyo., speaks to reporters after House Republicans voted to oust her from her leadership post as chair of the House Republican Conference at the Capitol in Washington, Wednesday, May 12, 2021. (AP Photo/J. Scott Applewhite)

Rep. Liz Cheney, R-Wyo., speaks to reporters after House Republicans voted to oust her from her leadership post as chair of the House Republican Conference at the Capitol in Washington, Wednesday, May 12, 2021. (AP Photo/J. Scott Applewhite) (AP Photo/J. Scott Applewhite)

"What happened on January 6th can never happen again," Cheney said in a statement. "Those who are responsible for the attack need to be held accountable and this select committee will fulfill that responsibility in a professional, expeditious, and non-partisan manner."

Pelosi announced her eight choices for the 13-member committee Thursday at a Capitol news conference. 

The chairperson will be Rep. Bennie Thompson, the chair of the Homeland Security Committee. Other Democratic members are Reps. Zoe Lofgren, the chair of House Administration Committee; Adam Schiff, chair of the Intelligence Committee, as well as Reps. Pete Aguilar of California, Stephanie Murphy of Florida, Jamie Raskin of Maryland and Elaine Luria of Virginia. 

PELOSI CREATES SELECT COMMITTEE TO INVESTIGATE JAN. 6 RIOT, SAYS ‘REPUBLICANS ARE AFRAID OF THE TRUTH’

Cheney later joined the Democratic committee members at the Capitol and expressed confidence in the work ahead. "It will be thorough, it will be professional, it will be serious, and not partisan," she told reporters. "I think this is something where we all have to come together."

McCarthy has yet to announce whether he'll make his designated five GOP appointments to the committee or withhold membership altogether. 

McCarthy said he's "not threatening anybody" with committee removal, but pointed out that Cheney broke tradition by seeking a committee assignment from the speaker when committee membership is decided by the leadership of a rep's own party.

U.S. House Speaker Nancy Pelosi (D-CA) is flanked by House Democratic leaders as she discusses the formation of a select committee to investigate the January 6 attack on the U.S. Capitol during her weekly news conference in Washington, U.S., July 1, 2021. REUTERS/Jonathan Ernst

U.S. House Speaker Nancy Pelosi (D-CA) is flanked by House Democratic leaders as she discusses the formation of a select committee to investigate the January 6 attack on the U.S. Capitol during her weekly news conference in Washington, U.S., July 1, 2021. REUTERS/Jonathan Ernst (Reuters)

"For somebody to accept committee assignments from Speaker Pelosi – that's unprecedented," McCarthy said Thursday of his former conference chairwoman.

He suggested that by accepting a committee assignment from the opposing party a Republican should no longer "expect" to have committee slots from their own party. Cheney currently sits on the powerful House Armed Services Committee. 

McCarthy also questioned whether Cheney was more closely aligned with Democrats. "I was shocked that she would accept something from Speaker Pelosi. It would seem to me since I didn't hear from her maybe she's closer to her than to us."

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The Jan. 6 committee is charged with investigating the circumstances surrounding the "domestic terrorist attack" and issuing a final report with recommendations for corrective measures. There's no timetable for the work to be completed, meaning the committee could keep the Jan. 6 attack in the headlines well into the 2022 midterm election year.

Fox News' Tyler Olson contributed to this report.