Adam Schiff, a California Democrat, said the memo of the call that the White House released earlier on Wednesday in which Trump asked Ukraine to investigate former Vice President Joe Biden, currently seeking the Democratic presidential nomination, sounded like threats made by the mafia.
"What those notes reflect is a classic mafia-like shakedown of a foreign leader," the Congressman said.
He is also the chair of the House Intelligence Committee which is seeking an interview with the original whistleblower.
Democrats in the U.S. House of Representatives on Tuesday launched a formal impeachment inquiry into President Donald Trump, accusing him of seeking foreign help to smear Democratic rival Joe Biden ahead of next year's election.
The inquiry ensures a partisan fight in Congress and on the presidential campaign trail in coming months, energizing the most committed Republican and Democratic supporters and overshadowing the Democratic race for the nomination to face Trump in the November 2020 election.
House Speaker Nancy Pelosi announced the inquiry after a closed-door meeting with Democratic lawmakers, saying Trump's actions undermined national security and violated the U.S. Constitution.
"The president must be held accountable.
No one is above the law," said Pelosi, who for months had been reluctant to embrace an impeachment effort.
Trump fired back quickly on Twitter, calling the inquiry "Witch Hunt garbage."