Senate Minority Leader Chuck Schumer is demanding that Speaker Paul Ryan remove Rep. Devin Nunes as chairman of the House Intelligence Committee if he wants to ensure a "credible" investigation into ties between Russian officials and the Trump campaign.

The New York Democrat said Nunes' visit to the White House last week raises serious questions about his ability to run an impartial investigation and follow the facts where they lead.

"Chairman Nunes is falling down on the job and seems to be more interested in protecting the president than seeking the truth," Schumer said in remarks on the Senate floor Monday. "You cannot have the person in charge of an impartial investigation be partial to one side. It's an inherent contradiction."

"If Speaker Ryan wants the House to have a credible investigation, he needs to replace Chairman Nunes," Schumer said. He added that Nunes is "pushing the committee into a direction of obsequiousness" to President Trump and his administration officials.

Nunes confirmed earlier Monday that he visited the White House last week the day before he announced that he has uncovered evidence that intelligence agencies had "incidentally" caught Trump campaign officials in a surveillance dragnet. A spokesman said he was on the White House grounds to meet a source who showed him secret American intelligence reports about the surveillance.

He said he was there because he needed access to a secure facility, known as a SKIF, to view classified information that the source provided.

Schumer and other Democrats say there are SKIFs in the Capitol building and other locations around Washington so he didn't need to go to the White House to view the classified material.

Nunes's spokesman on Monday also pointed out that his boss is also focused on the possible unmasking of names of U.S. citizens, and began looking into the issue before President Trump tweeted that Trump Tower had been "wiretapped."

Schumer dismissed Nunes' arguments, accusing him on ruining decades of bipartisanship on the intelligence panels.

"There has always been a good tradition of bipartisanship on the intelligence committees," he said. "When the members go into the SKIF…they check their partisanship at the door. Chairman Nunes is right on the edge of doing great damage to that tradition."