Top Congressional Democrats are expressing outrage after members of President Donald Trump’s administration inadvertently added Jeffrey Goldberg, the editor-in-chief of The Atlantic, to an unsecured message thread discussing highly sensitive war plans on Monday.

National Security Adviser Mike Waltz, who apparently added Goldberg to the Signal chat, was joined on the thread by those identified by Goldberg as Defense Secretary Pete Hegseth, Vice President JD Vance and Secretary of State Marco Rubio — among others.

Senate Minority Leader Chuck Schumer responded forcefully on the chamber floor on Monday, calling upon Leader John Thune and Senate Republicans to work with Democrats in calling a “full investigation” into why officials had coordinated military operations over Signal, rather than using taxpayer-funded secure communications channels.

“Mr. President, this is one of the most stunning breaches of military intelligence I have read about in a very, very long time,” Schumer said.

“What we have here are senior U.S. leaders, including the Vice President and Secretary of Defense, having classified discussions of military action over an unsecure app,” Schumer continued. “It’s bad enough that a private citizen was added to this chain, but it’s far worse that sensitive military information was exchanged on an unauthorized application, especially when that sensitive military information was so so important.”

“This kind of carelessness is how people get killed. It’s how our enemies can take advantage of us. It’s how our national security falls into danger,” he added.

The Democratic leader said that the investigation he’s called for should look into how this “debacle” happened, the damage it created, and how they could avoid it in the future.

“Every single Senator– Republican and Democrat and Independent, must demand accountability. If a government employee shared sensitive military plans like this, they’d be investigated and face very harsh consequences,” Schumer said.

He also suggested that his Republican colleagues should be as “outraged” by this incident as they were over the email controversy involving former Secretary of State Hillary Clinton in the days before the 2016 election, which she lost to Trump.

“If you were up in arms over unsecure emails years ago, you should certainly be outraged by this amateurish behavior,” Schumer said.

Schumer ended his brief remarks by claiming that Democrats has anticipated an event like this one when they opposed Hegseth’s nomination.

“When Pete Hegseth came before the Senate as a nominee, Democrats warned that something like this might happen. These people are clearly not up for the job. we warned confirming them was dangerous, that they behaved recklessly. Unfortunately, we were right. Now, we must have accountability in both parties. The Senate should investigate how this blunder was even possible,” Schumer said.

Clinton also reacted. “You have got to be kidding me,” she posted on X on Monday.

House Minority Leader Hakeem Jeffries also advocated for a congressional investigation and directly called out Hegseth.

“There should absolutely be a congressional investigation so that we can understand what happened. Why did it happen, and how do we prevent this type of national security breach from ever happening again,” Jeffries said at a press conference on Monday.

Jeffries, who got fired up when asked about the incident, called the situation “reckless, irresponsible and dangerous” and suggested that those involved were “jeopardizing America’s national security” — before sharply criticizing Hegseth.

“This whole Trump administration is filled with lackeys and incompetent cronies. I’m not talking about any particular individual, though,” he said. “I will note that the secretary of Defense who was on that chain has got to be the most unqualified person ever to lead the Pentagon in American history. Think about that.”

Speaker Mike Johnson downplayed the flurry of national security concerns on Monday afternoon.

“Look, I’m not going to characterize what happened. I think the administration has acknowledged it was a mistake, and they’ll tighten up and make sure it doesn’t happen again. I don’t know what else you can say about,” he told reporters at the Capitol, following a White House event where he appeared alongside Trump and the governor of Louisiana.

Johnson added that he doesn’t believe Waltz or Hegseth should be disciplined for the incident.

In addition to his on-camera remarks, Jeffries released a statement on the national security breach, calling it “completely outrageous.”

“It is yet another unprecedented example that our nation is increasingly more dangerous because of the elevation of reckless and mediocre individuals, including the Secretary of Defense,” Jeffries said.

He reiterated his call for a Congressional investigation into the matter — even though Democrats have little power to do so since they are in the minority.

“If House Republicans are truly serious about keeping America safe, and not simply being sycophants and enablers, they must join Democrats in a swift, serious and substantive investigation into this unacceptable and irresponsible national security breach,” he concluded.

Speaking to reporters in Honolulu on Monday, during a layover for a trip to Asia, Hegseth disputed Goldberg’s description of the chat, saying “nobody was texting war plans.”

Trump said he “doesn’t know anything about it” when first asked about the reports on Monday afternoon. The Pentagon referred questions to the National Security Council and the White House.

When asked by ABC News on Monday, the White House said that the Signal chat “appears to be authentic.” Additionally, White House National Security Council spokesman Brian Hughes shared with ABC News the statement he provided to The Atlantic confirming the veracity of a Signal group chat.

Both the top Republican and top Democrat on the Senate Armed Services Committee said Monday that they expect to receive classified briefings aimed at addressing the incident.

ABC News’ Fritz Farrow, Jay O’Brien, Lauren Peller and T. Michelle Murphy contributed to this report.