A simmering dispute between leaders of the House intelligence committee spilled into the public Monday over an investigation into whether President Donald Trump has ties to Russia, even as they pledged to conduct a bipartisan probe.

The Republican committee chairman, Rep. Devin Nunes of California, said he has heard no evidence so far that anyone in Trump's orbit was in contact with Russians during the presidential campaign. The top Democrat on the committee, Adam Schiff, also of California, said the committee's investigation was hardly off the ground and it was premature to make any conclusions.

The nature of ties between Trump's associates and Russia has dogged him throughout his nascent presidency, and Monday brought renewed calls for a special prosecutor to investigate the unusual situation. Federal investigators have been looking into contacts between Trump advisers and Russia for months, along with Russia's role in political hacking during the campaign aimed at Democrats. Trump, on Monday, said he hasn't called Russia in 10 years.

The House and Senate intelligence committees are conducting separate investigations. But revelations last week that the White House enlisted the chairmen of those committees to push back against news reports have intensified concerns over whether the congressional investigations will be tainted by political influence. The issue was likely to come up at Tuesday's Senate confirmation hearing for former Rep. Dan Coats, Trump's pick to be the next director of intelligence.

Speaking to reporters Monday, Nunes — a member of Trump's presidential transition team — said Congress should not begin a McCarthy-style investigation based on news reports that a few Americans with ties to Trump had contacted Russians during the 2016 presidential campaign.

"I want to warn all of you," Nunes said. "We can't have McCarthyism back in this place. We can't have the government, the U.S. government or the Congress, legislative branch of government, chasing down American citizens, hauling them before the Congress as if they're some secret Russian agent."

Former Sen. Joe McCarthy led a hunt for communists in the 1950s that was fueled by anonymous informants. Nunes said if evidence surfaces, the committee will investigate.

Schiff, who worked as an assistant U.S. attorney for six years, said it's not proper to start an investigation by stating your views of the outcome.

"The committee has reached no conclusion on whether the Trump campaign colluded with Russia, Russian officials or any Russian contacts — nor could we," Schiff said. "We have called no witnesses thus far. We have obtained no documents on any counterintelligence investigation and we have yet to receive any testimony from the FBI of potential links between the Trump campaign and Russia."

White House spokesman Sean Spicer said Russia's activity with regard to the 2016 election has been "investigated up and down."

"If there's nothing to further investigate, what are you asking people to investigate," Spicer said.

Trump was asked Monday whether he would support a special prosecutor to investigate Russia's influence on the 2016 election. Instead of answering that question, he said, "I haven't called Russia in 10 years." Trump did not say why he called Russia a decade ago.

According to a White House description, the last time Trump spoke by phone with Russian President Vladimir Putin was Jan. 28 and the White House said Putin had initiated the call. Trump also traveled to Russia in 2013 for the Miss Universe beauty pageant in Moscow.

Trump has denied knowing that any of his campaign advisers were in contact with Russians during the campaign. He has also said he has no financial ties or other connections to Russia.

Previously, mostly Democrats have requested a special prosecutor, but Republican Rep. Darrell Issa late Friday said Attorney General Jeff Sessions — who worked on Trump's presidential campaign — is not in a position to oversee such an investigation and urged the administration to appoint an independent prosecutor. Issa became the first Republican to break ranks on the subject, although House Speaker Paul Ryan said again Monday there should be no special prosecutor.

"The proper place, in my opinion, is the intelligence committees. They're the ones that have access to methods of intelligence gathering."

Sessions on Monday told reporters the FBI and Justice Department will remain independent.

"I would recuse myself from anything that I should recuse myself on," Sessions said. "That's all I can tell you."

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Democratic Sen. Richard Durbin, of Illinois, also said a special prosecutor was needed. Durbin noted on MSNBC that any report the intelligence committees produce as a result of their investigations would likely be initially classified, and the Trump administration would be responsible for declassifying portions and releasing them to the public.

Conducting the investigation in the Republican-controlled Senate intelligence committee "guarantees the American people will not know what is said," Durbin said.