The House Intelligence Committee's chairman, Devin Nunes, right, with the committee's ranking member, Adam Schiff. Mark Wilson/Getty Images The House Intelligence Committee's ranking Democrat on Monday called on the committee's Republican chairman to recuse himself from the committee's investigation into President Donald Trump's connections with Russia.

The statement by Rep. Adam Schiff followed news reports that Rep. Devin Nunes, the committee's chairman, had visited the White House grounds with a source who showed him secret intelligence reports the day before he briefed Trump that Trump and his advisers may have had their communications picked up "incidentally" as part of intelligence-community surveillance of foreign targets.

"After much consideration, and in light of the chairman's admission that he met with his source of information at the White House, I believe that the chairman should recuse himself from any further involvement in the Russia investigation, as well as any involvement in oversight of matters pertaining to any incidental collection of the Trump transition, as he was also a key member of the transition team," Schiff said in a statement.

Schiff said he worried the public was losing faith in Nunes' ability to conduct an unbiased investigation.

"I believe the public cannot have the necessary confidence that matters involving the president's campaign or transition team can be objectively investigated or overseen by the chairman," Schiff said.

House Minority Leader Nancy Pelosi echoed Schiff's sentiments and those of other Democrats who had increasingly been urging Nunes to step aside.

"The chair of the House Intelligence has a serious responsibility to the Congress and to the country," she said. "Chairman Nunes' discredited behavior has tarnished that office."

House Minority Leader Nancy Pelosi with other House Democrats at a news conference in the US Capitol on Friday in Washington, DC. Chip Somodevilla/Getty Images

"Speaker Ryan must insist that Chairman Nunes at least recuse himself from the Trump-Russia investigation immediately," Pelosi said. "That leadership is long overdue."

Nunes defended his White House visit by saying he wanted "to have proximity to a secure location" where he could view information provided by a source. The Trump administration was not aware of his visit, he said.

Democrats have seized on Nunes' announcement, accusing the Republican of attempting to give political cover for Trump, who claimed in a series of shocking, unsubstantiated tweets in early March that President Barack Obama had wiretapped Trump Tower during last year's presidential campaign.

Last week, Schiff said Nunes' actions had thrown "great doubt" on the committee’s ability to conduct a fair investigation.

Numerous lawmakers have called for a select committee to carry out the investigation, and the effort received bipartisan support when Republican Sen. John McCain questioned Nunes' credibility in an interview on Wednesday.

Trump appeared to complain about controversy surrounding Nunes on Monday night. In a series of tweets, the president said, "Why isn't the House Intelligence Committee looking into the Bill & Hillary deal that allowed big Uranium to go to Russia, Russian speech money to Bill," referring to Bill and Hillary Clinton.

The Washington Post reported in October last year that there was no evidence Clinton was personally involved in the uranium deal, to which Trump had previously referred.

Trump called the Russia investigation a "hoax" and has denied his team had any untoward interactions with the Kremlin. The FBI — along with the House and Senate intelligence committees and the Senate Judiciary Committee — are investigating whether Trump or his associates colluded with Russia during the 2016 campaign.

Read Schiff's entire statement below: