House Intelligence Committee chairman Devin Nunes is now himself under investigation by the House Ethics Committee. The panel is looking into claims that the Republican disclosed classified intelligence, Joinfo.com reports with reference to the BBC.
Mr Nunes called the charges “entirely false” and “politically motivated”.
He said his decision to step aside came after “several left-wing activist groups have filed accusations against me with the Office of Congressional Ethics”.
Mr Nunes added he would continue to fulfil his other responsibilities as chairman, requesting to speak to the ethics panel “in order to expedite the dismissal of these false claims”.
Democrats have criticised Mr Nunes for his handling of the inquiry, which is also looking at possible links between the Trump campaign and Moscow.
What did Mr Nunes allegedly do wrong?
The House Ethics Committee said in a statement on Thursday: “The Committee is aware of public allegations that Representative Devin Nunes may have made unauthorised disclosures of classified information, in violation of House rules, laws, regulations, or other standards of conduct.”
Watchdog groups Democracy 21 and Citizens for Responsibility and Ethics in Washington had asked the House ethics panel to investigate Mr Nunes.
His political foes have accused him of helping the White House to divert attention from several investigations into links between the Trump team and Russian officials.
Mr Nunes has acknowledged making an after-dark trip to the White House grounds last month that even the congressman’s own aides were apparently unaware of.
The next day at a hastily arranged news conference he announced he had learned that post-election communications of Mr Trump’s team had been monitored by US intelligence agencies as they snooped on foreign officials.
He expressed alarm that information about the then-incoming president’s aides had been swept up in US intelligence reports.
Mr Nunes’ Democratic colleagues on the panel were furious that he had not shared such information with them before going public.
In the face of much scepticism, Mr Nunes maintains White House officials were not his original source for the claims.
Democrats questioned whether the investigation into Russia’s alleged role in the election could proceed objectively.
House Speaker Paul Ryan said he fully supported Mr Nunes’ decision.
Mr Ryan said he trusts Mr Nunes, but the ehtics inquiry “would be a distraction” for the House Intelligence Committee investigation.
Representative Adam Schiff, a ranking Democrat on the House Intelligence Committee, said he respected Mr Nunes’ decision.
“We have a fresh opportunity to move forward in the unified and nonpartisan way that an investigation of this seriousness demands,” he added.
A White House spokesman said in response to the announcement: “This is an internal matter for the House”.
Texas Representative Mike Conaway will take over that inquiry with the help of fellow Republicans Trey Gowdy and Tom Rooney.
“We’re going to proceed with the investigation and follow every lead to its logical conclusion,” Mr Conaway said on Thursday.