House Republicans are investigating Michael Atkinson, the Intelligence Community inspector general who notified Congress of the whistleblower complaint that sparked an impeachment effort against President Trump.

California Rep. Devin Nunes, the ranking member on the House Intelligence Committee, told The Sara Carter Show on Monday that Atkinson still faces "serious questions" after his testimony in October, which to this day remains under wraps. Democrats have not released the transcript of that deposition despite mounting pressure by Republicans.

"Everyone needs to see that testimony," Nunes said, adding that the reason it has not been released is "because it's very damaging, not only to the whistleblower but also to Atkinson himself."

Nunes said House Republicans have "an active investigation" open into Atkinson. They have sent a letter to the inspector general, but Nunes said they "gave us a very typical IC response, which is to not answer the question." He also conceded that, as the minority party in the House, Republicans cannot subpoena Atkinson or force him to testify again.

A representative for Atkinson declined to comment for this report.

Atkinson received the complaint from a CIA analyst, whose identity has not yet been confirmed, in August and deemed it to be urgent and credible. The complaint raised concerns about Trump's July 25 phone call with Ukrainian President Volodymyr Zelensky, in which the Trump pressed for an investigation into his political rival Joe Biden. It also raised concerns about an effort to conceal details of that conversation and others using a highly secure computer system.

Atkinson forwarded the complaint to acting Director of National Intelligence Joseph Maguire, who did not give the watchdog permission to share it with Congress after seeking guidance from the White House and the Justice Department, but it did allow him to notify them of its existence. After a clash over access with Democratic lawmakers, the complaint was declassified on Sept. 25, the same day the transcript of the Trump-Zelensky call was released, and it was made available to the public the next day.

Republicans have complained that House Intelligence Committee Chairman Adam Schiff, who had a leading role in the House impeachment process, had foreknowledge of the whistleblower's complaint and misled them about what he knew. With some allies of Trump pointing the finger at CIA analyst Eric Ciaramella, the whistleblower's lawyers and Democrats have argued that the whistleblower's identity is no longer relevant and that outing the whistleblower would put that person's life in danger.

After testimony by dozens of witnesses, the House passed two articles of impeachment nearly three weeks ago that charged Trump with abuse of power in dealing with Ukraine and obstruction of Congress.

House Speaker Nancy Pelosi, a Democrat from California, has been withholding articles of impeachment because Senate Majority Leader Mitch McConnell has signaled he may not call any witnesses. The Kentucky Republican said he will not agree in advance to the Democrats' demands.