WASHINGTON >> House intelligence chairman Devin Nunes went to the White House grounds to review intelligence reports and meet the secret source behind his claim that communications involving associates of President Donald Trump were caught up in “incidental” surveillance, the Republican congressman said today.

Nunes’ revelation prompted the top Democrat on the committee, Rep. Adam Schiff, as well as the Democratic leaders in the House and Senate, to call on Nunes to recuse himself from the committee’s Russia probe.

Schiff said Nunes’ connections to the White House have raised insurmountable public doubts about whether the committee could credibly investigate the president’s campaign associates.

“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 in a statement.

Nunes confirmed today that he met with the source at the White House complex, but he denied coordinating with the president’s aides.

After reviewing the information last week, Nunes called a news conference to announce that U.S. spy agencies may have inadvertently captured Trump and his associates in routine targeting of foreigners’ communications. Trump quickly seized on the statements as at least partial vindication for his assertion that President Barack Obama tapped his phones at Trump Tower — though Nunes, Schiff and FBI Director James Comey have said there is no such evidence.

The Senate intelligence committee is also conducting an investigation into Russia’s interference in the election and possible ties with the Trump campaign. Today it announced that Trump’s son-in-law, Jared Kushner, has agreed to be interviewed. The White House confirmed that Kushner, a senior Trump adviser, had volunteered to be interviewed about arranging meetings with the Russian ambassador and other officials.

Kushner is the fourth Trump associate to offer to be interviewed by the congressional committees looking into the murky Russia ties. Trump’s former campaign chairman, Paul Manafort, Trump adviser Carter Page and Trump associate Roger Stone last week volunteered to speak as well.

“Mr. Kushner will certainly not be the last person the committee calls to give testimony, but we expect him to be able to provide answers to key questions that have arisen in our inquiry,” the chairman, Sen. Richard Burr of North Carolina, and the top Democrat, Mark Warner of Virginia, said in a joint statement in a sign of bipartisanship.

Trump himself suggested that the House panel should investigate Bill and Hillary Clinton’s dealings with Russia. “Trump Russia story is a hoax,” he tweeted.

Besides the two congressional committees, the FBI is also investigating connections between the Trump campaign and Russia.

The House investigation, meanwhile, has been plagued with partisan divisions under Nunes’ leadership.

The chairman did not tell top Democrat on the committee about the meeting at the White House complex. It is highly unusual for a committee chairman and ranking member not to coordinate meetings related to an investigation.

“‘I think the chairman has to make a decision whether to act as a surrogate of the White House — as he did during the campaign and the transition — or to lead an independent and credible investigation,” Schiff said Sunday on CBS’ “Face the Nation.”

Nunes argued he had to review classified, executive branch documents from a secure facility at the White House because the reports had not been provided to Congress and could not be transported to the secure facilities used by the House intelligence committee.

“Because of classification rules, the source could not simply put the documents in a backpack and walk them over to the House Intelligence committee space,” Nunes spokesman Jack Langer said. “The White House grounds was the best location to safeguard the proper chain of custody and classification of these documents, so the chairman could view them in a legal way.”

Nunes would not name the source of the information, nor would he disclose who invited him on the White House grounds for the meeting. In addition to the White House itself, the grounds include an adjacent building with offices for National Security Council and other executive branch employees.

Nunes described the source as intelligence official, not a White House official. In an interview on CNN, he suggested the president’s aides were unaware of the meeting.

White House spokesman Sean Spicer would not comment on whether White House officials were involved with Nunes.

“I’m not going to get into who he met with or why he met with them,” Spicer said.

The clandestine meeting was remarkable for a committee that seeks to demonstrate bipartisanship, said Jonathan Turley, a law professor at George Washington University who has written extensively about separation of powers.

“Ideally, any meeting at the White House on a subject under investigation would have been done with the knowledge of the ranking member or his staff,” Turley said. “Because these committees are the least transparent in Congress, both parties have historically tried to be open with each other on contacts or meetings with agencies on key questions.”

The disclosure renewed calls for an independent committee to investigate the Russia ties.

Indeed, Senate Minority Leader Chuck Schumer called on House Speaker Paul Ryan to replace Nunes as chairman of the intelligence committee.

“He has not been operating like someone who is interested in getting to the unvarnished truth. His actions look like those of someone who is interested in protecting the president and his party,” Schumer said.

House Democratic Leader Nancy Pelosi said, “Chairman Nunes’ discredited behavior has tarnished that office,” and said Ryan should insist that Nunes “at least recuse himself” from the Russia probe.

AshLee Strong, a spokeswoman for Ryan, said the speaker has “full confidence that Chairman Nunes is conducting a thorough, fair and credible investigation.”

When Nunes disclosed the intelligence reports last week, he said what he reviewed had nothing to do with Russia, which could suggest that Trump associates were in touch with other foreign targets of U.S. intelligence surveillance in November, December or January.

“The chairman is extremely concerned by the possible improper unmasking of names of U.S. citizens, and he began looking into this issue even before President Trump tweeted his assertion that Trump Tower had been wiretapped,” Langer said.

It is unclear exactly what documents Nunes reviewed.

Nunes and Schiff have asked the FBI, CIA and National Security Agency for the names of officials who were cited in intelligence reports. The committee has said it is getting some of what it requested, but has not received everything.