Senior lawmakers were quick to lash out at President Donald Trump's summit with his Russian counterpart Monday, with some saying he has abrogated the responsibilities of his office.

Republicans were among those highly critical of Trump's first summit with Vladimir Putin, particularly over Trump's refusal to side with his intelligence community in their determination that Putin orchestrated a wide-ranging covert campaign aimed at hurting then-Democratic candidate Hillary Clinton's chance of winning the 2016 presidential race.

"The damage inflicted by President Trump’s naivete, egotism, false equivalence, and sympathy for autocrats is difficult to calculate. But it is clear that the summit in Helsinki was a tragic mistake," Senate Armed Services Committee Chairman John McCain said in a tersely-worded statement. "No prior president has ever abased himself more abjectly before a tyrant."

Outgoing Senator Bob Corker, the chairman of the Senate Foreign Relations Committee, told reporters on Capitol Hill he is "very disappointed and saddened" by the "equivalency" Trump gave between his intelligence community and Putin's words.

"They definitely interfered in our election," he said. "That’s not debatable. And again, I just don’t know what it is about the president that he continues to deny that it occurred. I get the feeling, first hand actually, that sometimes the president cares more about how a leader treats him personally."

During a joint press conference that followed hours of talks between the U.S. and Russian leaders, Trump told reporters that while he has "great confidence" in the U.S. intelligence community "President Putin was extremely strong and powerful in his denial today."

He continued his criticism of Special Counsel Robert Mueller's investigation into alleged Russian meddling and possible Trump campaign collusion, saying it "is a disaster for our country. I think it’s kept us apart. It’s kept us separated.”

"It’s ridiculous what’s going on with the probe,” said Trump, adding that he doesn't "see any reason why" Russia would have sought to sway the election.

Mark Warner, the ranking Democrat on the Senate intelligence committee called Trump’s comments a violation of his most essential duties as president.

“For the President of the United States to stand next to Vladimir Putin — who personally ordered one of the largest state-sponsored cyber-attacks in our history — and side with Putin over America’s military and intelligence leaders is a breach of his duty to defend our country against its adversaries,” he said in a statement.

Republican House Speaker Paul Ryan said there is no question Moscow interfered in the 2016 election.

"That is not just the finding of the American intelligence community but also the House Committee on Intelligence," he said in a statement. "There is no moral equivalence between the United States and Russia, which remains hostile to our most basic values and ideals. The United States must be focused on holding Russia accountable and putting an end to its vile attacks on democracy."

In one of the strongest rebukes to date, former CIA Director John Brennan said "Donald Trump’s press conference performance in Helsinki rises to & exceeds the threshold of 'high crimes & misdemeanors.'

"It was nothing short of treasonous. Not only were Trump’s comments imbecilic, he is wholly in the pocket of Putin. Republican Patriots: Where are you???" he wrote on Twitter.

Trump sought to defend his comments on the social media platform, saying he has "GREAT confidence in MY intelligence people.

"However, I also recognize that in order to build a brighter future, we cannot exclusively focus on the past – as the world’s two largest nuclear powers, we must get along!" he said.