Speaker Nancy Pelosi said the House of Representatives will look at whether Mr Trump sought Ukraine’s help to smear former Vice President Joe Biden, the front-runner for the 2020 Democratic presidential nomination. Ms Pelosi said: “Therefore today I’m announcing the House of Representatives is moving forward with an official impeachment inquiry.
“The President must be held accountable. No one is above the law.”
But Trump took to Twitter to slam the move, calling it “Witch Hunt garbage”.
He tweeted: “Such an important day at the United Nations, so much work and so much success, and the Democrats purposely had to ruin and demean it with more breaking news Witch Hunt garbage. So bad for our Country!
“Pelosi, Nadler, Schiff and, of course, Maxine Waters! Can you believe this?
“They never even saw the transcript of the call. A total Witch Hunt! PRESIDENTIAL HARASSMENT!”
It follows accusations that Trump had pressured Ukrainian President Volodymyr Zelenskiy in a phone call on July 25 to investigate Democratic presidential front-runner Joe Biden.
Trump has insisted that the move to impeach him is a complete “witch hunt”.
Tweeting to his followers, the President also argued that the Democrats had “never even saw the transcript of the call”.
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Dodging claims that he pressured Mr Zelensky to investigate Mr Biden, Trump revealed that he had authorised the release of the full transcript of the conversation.
Following that announcement, Trump insisted that the conversation was “a very friendly and totally appropriate call”.
The call to impeach the US President comes as Trump and his allies have pointed out that Mr Biden had threatened to withhold aid to Ukraine in 2016.
According to some, during his time as vice-President, Mr Biden had made the threat in order to force Ukraine to fire a prosecutor who had been investigating a natural gas company where his son, Hunter, was on the board.
However, Ukraine’s current prosecutor, Yuriy Lutsenko did insist that there had been no evidence of wrongdoing from Mr Biden or his son.
Speaking on the recent allegations Mr Biden said it “would be a tragedy” to impeach Trump.
He did, however, insist that the tragedy would be “of his own making”.
Since the news broke out, almost a dozen Democrats have come out in favour of impeachment over the last week since the controversy.
Although 145 House Democrats back the move, the Senate is unlikely to support the action as it is in Republican control.