The letter demanding that the panel preserve its records — a step already required — was the latest indication that the G.O.P. is planning its own counter-investigation into the Jan. 6 attack.
WASHINGTON — Representative Kevin McCarthy, the California Republican who is attempting to become the next House speaker, on Wednesday warned the special committee investigating the Jan. 6, 2021, attack on the Capitol that members of his party planned to launch an inquiry of their own into the panel’s work next year when Republicans assume control of the chamber.
In a letter sent to the committee’s chairman, Mr. McCarthy instructed the panel to preserve its records — an action already required under House rules — including any recorded transcripts of its more than 1,000 interviews. The missive was the first official indication that newly empowered House Republicans plan not only to end the inquiry at the start of the new Congress, but also to attempt to dismantle and discredit its findings — the latest piece of a broader effort the party has undertaken over the past two years to deny, downplay or shift blame for the deadly attack by a pro-Trump mob.
It comes as Mr. McCarthy toils to shore up his position with hard-right Republicans in his conference who have refused to support his bid for speaker, imperiling his chances of being elected in January.
Mr. McCarthy pledged in the letter that he would hold public hearings scrutinizing the security breakdowns that occurred during the assault, when a pro-Trump mob stormed the Capitol, disrupting Congress’s formal count of electoral votes to confirm Joseph R. Biden Jr.’s election as president.
“Although your committee’s public hearings did not focus on why the Capitol complex was not secure on Jan. 6, 2021, the Republican majority in the 118th Congress will hold hearings that do so,” Mr. McCarthy wrote to Representative Bennie Thompson, Democrat of Mississippi and chairman of the committee
The committee, which will be dissolved at the end of the current Congress, is finishing up its final batch of witness interviews, including a session on Wednesday with Robin Vos, the speaker of the Wisconsin State Assembly, who said former President Donald J. Trump has continued to try to pressure lawmakers to overturn the 2020 election — even more than a year after his defeat.
The panel is also completing an extensive report, which is expected to be released in December and is the subject of much internal debate over how much to focus on Mr. Trump’s actions versus security failures at the Capitol. Members of the committee’s so-called Blue Team have conducted months of investigation and research into such failures, but it was unclear how much of their work would be featured.
Mr. McCarthy highlighted the complaints raised by some current and former staffers in media reports that their work investigating security failures, the financing of the rallies that preceded the attack and the threat of white nationalism would be overshadowed in the report by a focus on Mr. Trump’s attempts to overturn the 2020 election.
Lawmakers on the committee have said they are attempting to create a readable report — and had to make difficult choices about what to include, given the voluminous evidence accumulated — but plan to release the full transcripts of their interviews after making some redactions to prevent the identification of witnesses who were granted anonymity.
In addition to interviewing more than 1,000 witnesses, the committee has obtained more than one million pages of documents.
Shortly after the attack, both the Senate and the House held multiple hearings investigating security failures, and the Senate produced a bipartisan report detailing those failures.
Republicans, especially those on the hard right, have pressed to focus on the security flaws, which they have baselessly blamed on Speaker Nancy Pelosi, rather than on Mr. Trump’s role in pushing for the election to be overturned and summoning a large crowd to march on the Capitol, where they attacked and injured more than 150 police officers in a bloody rampage.
In a recent closed-door meeting of Republicans, right-wing lawmakers including Representative Marjorie Taylor Greene of Georgia also extracted a promise that their leaders would investigate Ms. Pelosi and the Justice Department for their treatment of defendants jailed in connection with the Jan. 6 attack.
Mr. McCarthy has long derided the Jan. 6 committee’s investigation. He refused to comply with a subpoena and has argued the panel is “illegitimate” because Ms. Pelosi rejected two of his nominees.
The panel has taken no step to enforce that subpoena, citing congressional traditions.