The man tasked with leading the US probe into potential Russian interference in last years' Presidential election is now himself, under investigation.
Devin Nunes has been accused of making unauthorised disclosures of classified information in violation of House rules.
The Republican says he chose to step down in the hope it will fast-track dismissal of the allegations, which he says are "entirely false."
He accused several "left-wing activist groups" of filing the allegations against him with the Office of Congressional Ethics.
Speaking to reporters aboard Air Force One, US President Donald Trump praised Mr Nunes for his decision.
"I think he's a very good person. I just heard that he did. He's a very good person, he's a very honorable guy. And I think he did that maybe for his own reason. He's a high quality person."
The investigation led by Mr Nunes is one of several in Congress looking into whether Russia tried to influence the election in President Donald Trump's favour.
But critics have accused Mr Nunes of helping the White House to divert attention.
The accusations him date back to March when President Trump claimed he was wiretapped by the Obama administration without providing evidence.
Mr Nunes acknowledged making a secret, after-dark trip to the White House grounds last month.
Then, weeks later, he held a news conference saying an unidentified source had shown him intelligence reports containing names of Trump associates apparently caught up in routine domestic foreign surveillance.
But Mr Nunes denies any wrongdoing.
"Details about US persons associated with the incoming administration, details with little or no apparent foreign intelligence value, were widely disseminated in intelligence community reporting. Third, I have confirmed that additional names of Trump transition team members were unmasked. Fourth, and finally, I want to be clear, none of this surveillance was related to Russia or the investigation of Russian activities or of the Trump team."
Both Russia and President Trump have dismissed the claims and Speaker of the House, Paul Ryan says he supports Mr Nunes' decision, saying the probe into him would be 'distraction' from the Russia investigation.
"Devin Nunes has earned my trust over many years for his integrity and dedication to the critical work that the intelligence community does to keep America safe. He continues to have that trust, and I know he is eager to demonstrate to the Ethics Committee that he has followed all proper guidelines and laws. In the meantime, it is clear that this process would be a distraction for the House Intelligence Committee's investigation into Russian interference in our election.
The top Democrat on the committee, US Representative Adam Schiff says having Mr Nunes out of the picture will give the investigation an opportunity for a "fresh start".
"I'm sure it was a very difficult decision for him. But as he mentioned, I think it was in the best interest of the investigation. It will I think allow us to have a fresh start moving forward. This investigation is of such critical importance that we need to get fully back on track."
Representative Mike Conaway, the most senior Republican on the intelligence committee, will replace Devin Nunes.
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