: "If the president is essentially withholding military aid at the same time that he is trying to browbeat a foreign leader to do something illicit, to provide dirt on his opponent during a presidential campaign, then that (impeachment) may be the only remedy that is co-equal to the evil that conduct represents."
He also said on Twitter: "An explicit quid pro quo isn’t required to betray your country. It’s enough to abuse power for personal gain.
"Giuliani doing it is bad enough. Trump is a different matter. It’s one thing when it’s done by the court jester, and another when done by the man who would be King."
Members of Congress are also looking into whether lawyer Rudy Giuliani went to the Ukraine in order to pressure the government to aid Trump's re-election by investigating the activities of Biden's son.
'OVERWHELMING ABUSE OF POWER' It is unclear what allegations may have been levelled against 49-year-old Hunter - who had worked for Burisma Holdings, a major Ukrainian gas company.
The shocking revelations - first reported by the - prompted a furious response from the former Vice President.
Democrat 2020 frontrunner Joe , 76, said in a scathing statement on Friday that if the reports are true, "then there is truly no bottom to President Trump's willingness to abuse his power and abase our country."
He added that Trump should release the transcript of his July phone conversation with President Volodymyr Zelenskiy "so that the American people can judge for themselves" and accused the president of “overwhelming abuse of power”.
The worrying claims are now at the heart of an explosive - but still confidential - whistleblower complaint against Trump.
'SIGNIFICANT' WHISTLE BLOWER CLAIMS An anonymous intelligence official raised concerns on August 12 to the government's intelligence inspector general.
Those claims - described as "serious" and "urgent" - involve the "most significant" responsibilities of intelligence leadership.
But a defiant President Trump dismissed the allegations on Friday as originating from a "partisan whistleblower."
Trump insisted the unspecified allegations as "nothing" and "just another political hack job" - while scolding reporters for asking about it.
Speaking at the Oval Office, Trump added: "I have conversations with many leaders. It's always appropriate. Always appropriate.
"At the highest level always appropriate. And anything I do, I fight for this country."
Democrats are calling for access to further details of the whistleblower's complaints amid allegations of a White House cover-up.
Mr Schiff asked: "If there's nothing wrong with Trump's call with the Ukrainian President, as he claims, why won’t he release the transcript?
"If there's nothing to implicate Trump in the whistleblower complaint, why won’t they release it to Congress?
"Clearly, they’re afraid. We must see both."
Joe Biden called for the release of the transcripts of President Trump's call to his Kiev counterpart in July Credit: Getty Images - Getty President Trump allegedly pressured Ukraine's President Volodymyr Zelenskiy to investigate Hunter Biden Credit: AFP or licensors
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