WASHINGTON — Top Democrats on Thursday excoriated President Donald Trump after his former attorney Michael Cohen pleaded guilty to lying to Congress about efforts to build a Trump Tower in Moscow during the presidential campaign.

Sen. Kirsten Gillibrand, D-N.Y., said there is a "culture of corruption" surrounding Trump and renewed calls to protect special counsel Robert Mueller, who brought the bombshell charges against Cohen on Thursday morning in Manhattan federal court as part of his investigation into Russian election meddling.

"There is a culture of corruption surrounding @realDonaldTrump and his administration. It is absolutely critical for Congress to protect the Mueller investigation and ensure the American people get the answers and justice they deserve," Gillibrand said in a tweet.

There is a culture of corruption surrounding @realDonaldTrump and his administration. It is absolutely critical for Congress to protect the Mueller investigation and ensure the American people get the answers and justice they deserve. https://t.co/ScX4hbedRY — Kirsten Gillibrand (@SenGillibrand) November 29, 2018

Cohen, 52, named Trump and his private business dealings in Moscow in open court as part of Mueller's investigation into Russia's ties to the Trump campaign. Throughout the 2016 campaign, Trump denied having business interests in Russia. But Cohen said in his plea that those business interests were not severed and in fact continued into the summer of 2016.

Prosecutors said Cohen lied to the Senate Select Committee on Intelligence in order to minimize links between Trump and his Moscow building project and to give the false impression that the project had ended before the Iowa caucuses, which took place in February of 2016.

Sen. Mark Warner, D-Va., the vice chairman of that committee, said Cohen's admission is just another example of one of Trump's "closest allies lying about their ties to Russia and Russians."

"You've got all these close associates of the president, one after another, pleading guilty, often pleading guilty about their ties to Russia and Russians, and what are they covering up for?" Warner added.

He said Cohen was "obviously" one of the witnesses "we've always wanted to have come back" before the committee.

Rep. Adam Schiff, D-Calif., the incoming chairman of the House Intelligence Committee, called Cohen's deal a "very significant plea and statement" and suggested that there were others who possibly lied to congressional investigators.

"It means that when the president was representing on the campaign that he has no business interests in Russia, that that wasn't true," Schiff said. "This, I think, only underscores I think the importance of not only bringing Mr. Cohen back before our committee but also looking into this issue of whether the Russians possess financial leverage over the president of the United States."

He added: "But I think Michael Cohen’s guilty plea underscores something else, and that is we believe other witnesses were untruthful before our committee. We want to share those transcripts with Mr. Mueller."

The House Intelligence Committee was bitterly divided in its separate Russia probe. The committee formally ended its Russia investigation this past March, voting along partisan lines to release a final report that asserts there was no evidence of collusion involving the Trump campaign and Russia.

The committee issued a 250-page classified report to the nation’s intelligence agencies but made public a summary of 44 findings.

The committee was largely led by Trump loyalist Rep. Devin Nunes of California before he temporarily stepped aside in April 2017 amid a barrage of criticism and ethics complaints that he violated House rules by discussing classified information with the White House. He was cleared in December 2017 of violating any rules.

The Republicans on the committee fended off more than a dozen attempts by Democrats to prolong the probe by subpoenaing additional witnesses.

On Thursday, Schiff said that once he is chairman, he would "absolutely" release the transcripts of the committee interviews to the special counsel if Republicans do not do so.

Sen. Dianne Feinstein, D-Calif., the ranking member of the Senate Judiciary Committee and a member of the Senate Intelligence Committee, said in a statement on Thursday that Cohen's admission "raises serious questions about the president’s relationship with Russia and whether he and his family have been honest with the American people."

“Today's guilty plea clearly shows that we still don’t know the full story and that Special Counsel Mueller must be allowed to complete his investigation without interference or delay,” Feinstein said.

Rep. Jerry Nadler, D-N.Y., the ranking member of the House Judiciary Committee, said that Cohen's guilty plea is a serious offense and that he wants to know why he lied to Congress originally.

"He lied to Congress apparently about dealings between Trump and Russia. And that leads me to suspect that there are more dealings that the president wanted hidden," Nadler said. "And this raises all kinds of questions with respect to the question of how much — whether the Russian government has any kind of hold on the president because of his financial dealings and whether the president knew about the obvious collusion between his campaign and the Russians."

He said that he thinks it is a sign that Congress needs to step up and have "an honest investigation."

GOP says plea doesn't prove collusion

As Democrats again called for legislation to protect Mueller's investigation, Republicans were quick to note that Cohen's admission doesn't prove collusion between Trump's campaign and Russia.

House Speaker Paul Ryan, R-Wisc., reacted to the news in a forum with The Washington Post on Thursday morning, saying that Cohen should be prosecuted before defending the House Intelligence Committee's own Russia probe.

"Well, he should be prosecuted to the extent of the law," Ryan said of Cohen. "That’s why we put him under oath. I mean so just back it up for a second, lying to Congress. That means he came and testified. That means we swore him under oath. That means we put him on the record. That means we did our job."

He added that he wasn't concerned about Mueller not being allowed to complete his work.

"If I was really, really stressed about Bob Mueller I would do something. I’m not worried about Bob Mueller," he said.

Sen. Richard Burr, R-N.C., chairman of the Senate Select Committee on Intelligence, said Thursday that he had not seen Cohen's plea agreement, but noted: "this is a reason people shouldn’t lie when they're in front of a congressional investigation."

Some Republicans, like Sen. Lindsey Graham of South Carolina and Sen. John Thune of South Dakota, said Cohen's admission doesn't prove collusion between Russia and the president.

“I don't think at this point that there has been anything that, in any way, changes the landscape, so to speak, where the president is concerned," Thune said in an interview with Fox News Thursday. "He has argued all along there wasn't any collusion on the part of his campaign team or his administration with Russia. And I haven't seen anything that disproves that."

Thune added that the Mueller probe should be thorough and complete, but can’t go on forever. He said Trump has important work to do for the American people and it is time to "move on."

“And the longer these things drag on, it just, it gets, I think, very wearing on the American people,” he said. “The report needs to come out. We need to know what happened, but I agree with my colleagues that the time I think has come to start drawing this to a conclusion.”

Graham, who has emerged as one of Trump's fiercest defenders, said he had "no idea what that's all about" when asked his reaction to Cohen's guilty plea, adding that it "seems to be a process crime."

"I've yet to see anybody indicated for actually colluding with the Russians," Graham told reporters on Capitol Hill. "I don't know where Mueller is going but it is up to him to get there sooner rather than later."