Washington (CNN) House Intelligence Chairman Adam Schiff vowed Friday to mount an extensive investigation into the whistleblower controversy dominating Washington -- even as a growing number of Republicans were quick to dismiss the concerns that were allegedly raised about President Donald Trump's conduct.

The California Democrat said Congress will get to the bottom of why the mysterious whistleblower complaint is being withheld from lawmakers come "hell or high water," asserting that the case involves something "more sinister" than a policy difference.

"This involves something more sinister, something involving a serious or flagrant abuse or violation of law or misappropriation, and the IG underscored the seriousness of this, and also that this needs to be looked into. And right now, no one is looking into this," he said.

Schiff has maintained that he has yet to see the complaint itself and does not know the identity of the whistleblower.

House Speaker Nancy Pelosi publicly backed Schiff's push to obtain the complaint, telling CNN that the law is clear and she defers to the Intelligence Committee chairman's guidance on the matter. She would not however, confirm reporting by The Washington Post and New York Times that the complaint deals, at least in part, with Ukraine.

"The law says that the DNI should send the information -- shall, not should -- shall send that information to Congress. So the law is the law. So we just have to uphold the law," the California Democrat said.

"You know what? Why don't you talk to Adam Schiff, because he is our chair of that committee and is most familiar with what all the possibilities are and I'll be taking guidance from him," Pelosi added.

When asked about reports indicating the complaint involves communication between the President and a foreign leader, Democratic Rep. Alexandria Ocasio-Cortez of New York criticized members of her own party, including Pelosi, who she believes are moving too slowly on opening an impeachment inquiry into the President.

"We are getting deeper and deeper into a crisis, and I think at this point we are beyond a constitutional crisis. This is a threat to the very sovereignty of the United States, and I can't understate how concerning this is," she said Friday.

"I've said it before, I'll say it again: Impeachment is not something I want to do. It's not something I ran on, but when you have the President calling in from other countries and whistleblowers are talking about compromising who he has deemed a political enemy, this is serious. This is very, very serious. And we have to investigate it. And we have to stop the infighting and the arguments. We just need to do the work," Ocasio-Cortez added.

Republicans taking a different view

House Republicans appeared content to give Trump a pass on the controversy or avoid questions on the issue altogether on Friday.

Republican Rep. Matt Gaetz of Florida said he did not even need to review the complaint because he trusts the President and knows Trump did not do anything wrong.

"No need to assess" the complaint himself, Gaetz said. "Sometimes this town really is a lot like kindergarten. I think there are people in the intelligence community and other parts of our government who just have it out for the President."

Rep. Ted Yoho, a fellow Florida Republican, said "no" when asked if he had any concerns that part of the whistleblower complaint reportedly involves Trump making a promise to a foreign leader.

House Minority Leader Kevin McCarthy, a California Republican, turned questions around about the whistleblower: "He could have come to Congress. Who is the whistleblower? Is he still working? Because I don't know anything about him. I've heard rumors it's somebody who left. Why did he leave? And now this comes up."

Speaking to reporters Thursday afternoon, Schiff had said his committee was exploring legal options to obtain the whistleblower complaint

"This is not a situation where we can afford to go through weeks or months of litigation in this court or that court. There is an urgency here that I think the courts will recognize," he said. "I hope that's not necessary. And I hope that the director of national intelligence will reconsider."

He also pledged to "use whatever leverage we can. But at the end of the day, we are determined to validate the whistleblower process to make sure that people can expose wrongdoing."

The threat could deepen the controversy surrounding the complaint , which is at the center of a dispute between acting Director of National Intelligence Joseph Maguire and Congress.

Schiff and other congressional Democrats are growing more and more agitated with the White House and Maguire, who have blocked their access to the complaint. Democratic lawmakers contend that Maguire is violating the law in refusing to turn over the complaint, something his office disputes.

CNN reported on Thursday that the White House has been advising the nation's top intelligence agency the complaint is outside intelligence activities covered by laws governing intelligence whistleblowers, according to three sources familiar with the matter. During a closed-door briefing with Schiff's committee Thursday, Michael Atkinson, the intelligence community's inspector general, would only discuss the process for his handling of the whistleblower's concerns, the chairman said. Though lawmakers pressed him for details on the complaint, their efforts were ultimately unsuccessful.

The inspector general does not have the authority to discuss the details of the complaint with Congress because the DNI has not shared the actual report with the committee and had apparently not otherwise authorized Atkinson to share those details.

The intelligence whistleblower act does not allow for details to be provided until the actual complaint has been given to Congress, CNN legal contributor Steve Vladeck explained Thursday.

Although the official details of the complaint have not been provided to members of Congress, Atkinson told the panel during the briefing that it raised concerns about multiple actions but would not say if those instances involved Trump, according to sources familiar with the briefing.