To add insult to injury, Mr. Comey, along with Michael Rogers, the Director of the National Security Agency, also contradicted Mr. Trump's wildly irresponsible claims on Twitter that former president Barack Obama had ordered the wiretapping of Trump Tower in New York City during the election campaign.
Russian Federation has repeatedly denied attempting to influence the results by hacking Democratic operatives and releasing embarrassing information.
Monday's hearing, one of several by congressional panels probing allegations of Russian meddling, could allow for the greatest public accounting to date of investigations that have shadowed the Trump administration in its first two months.
"Because it is an open, ongoing investigation and is classified, I can not say more about what we are doing and whose conduct we are examining", he added.
FBI Director James Comey and National Security Agency Director Mike Rogers will testify on-the-record under oath starting at 9 a.m.
Earlier during the hearing, Senator Devin Nunes, the Republican chairman of the committee, debunked Mr Trump's claim that his predecessor listened in on his communications, but did not rule out other surveillance methods.
A senior US lawmaker says he has seen "no evidence" of collusion between President Donald Trump's campaign and Russian Federation during last year's presidential campaign.
"I think there's no question that the Obama administration, that there were actions about surveillance and other activities that occurred in the 2016 election", Spicer said. A recently declassified report from the Office of the Director of National Intelligence revealed that every USA intelligence agency concurred that Putin ordered a concerted effort to "undermine" democracy in America and boost Trump's chances of victory.
He moved on to say an investigation would now take place into "whether crime was committed", while insisting nobody is exempt from the law if it can be proven they were involved.
About two hours later, Trump asked in a tweet, "What about all of the contact with the Clinton campaign and the Russians?"
He also posted, "The real story that Congress, the Federal Bureau of Investigation and all others should be looking into is the leaking of Classified information". His appearances on Capitol Hill since then have occurred in classified settings, often with small groups of lawmakers, and he has made no public statements connected to the Trump campaign or Russian Federation.
The Senate Intelligence Committee will have a similar hearing later this month.
Stewart said "you would have to crawl inside someone's head" or have direct information to know their motivations.
Trump has said he has no knowledge of his associates coordinating with Russian Federation during the election.