Top House Democrat Adam Schiff told "CBS This Morning" Wednesday that what President Trump has admitted publicly about pressuring Ukraine to get information on a political adversary during a private call is "damning enough" to justify impeachment proceedings. Schiff, the chairman of the House Intelligence Committee, is leading just one of six impeachment investigations into Mr. Trump.

The call, during which Mr. Trump talked about former Vice President and 2020 Democratic presidential candidate Joe Biden and his son Hunter, is the subject of a whistleblower's complaint, which the intelligence community inspector general found both credible and of "urgent concern."

"That is a horrible abuse of the oath of office," said Schiff of the president's withholding of military aid to Ukraine before his call with Ukrainian president Volodymyr Zelensky.

"What the president has already admitted, the president's acknowledgement of withholding Ukraine aid, the fact that he would not share with leaders of his own party like Mitch McConnell the justification, the fact that when this came to light he has now given shifting explanations for why he withheld the aid, I think all those facts which are uncontested at this point compel us to move down the path of formal impeachment inquiry," Schiff said.

As a result of the revelations, the complaint was supposed to be turned over to the House Intelligence Committee, but the acting director of national intelligence, Joseph Maguire, has declined to submit the complaint to the committee because he determined that it was not of urgent concern. White House and intelligence agencies are now discussing ways to share information from that original complaint with lawmakers.

Schiff said the whistleblower now wants to testify before his committee, and said he wrote a letter to attorneys representing the individual to request a voluntary interview on Thursday. The Democrat noted, however, the whistleblower "is not the sum total of the story," suggesting that White House associates like Trump attorney Rudy Giuliani admitted that he "was also pressuring Ukraine to manufacture dirt on Joe Biden."

"There may have been many interactions by the president or people like Rudy Giuliani to apply this pressure campaign even as the president of the United States withheld vital military aid to an ally that's at war with Russia," said Schiff.

"The national security of the United states is very much at risk here," he added.

House Speaker Nancy Pelosi decried the president's most recent actions as a "betrayal of his oath of office" as she formally launched a formal impeachment inquiry of Mr. Trump.

Schiff said that lawmakers are now going to move expeditiously, saying there's no reason to wait for the release of the complaint to start impeachment proceedings.

For now, Mr. Trump maintains that a transcript of the call with Zelensky set to be released by the White House on Wednesday will exonerate him from any wrongdoing. He described the call as "perfect" and said there was no quid pro quo during the conversation. Schiff contends, however, that the transcript alone will not factor into lawmakers' decision-making process.

"What the president has already admitted is all we needed to know," he said.