Former White House aide Fiona Hill has told the impeachment inquiry that President Donald Trump disregarded the advice of senior advisers to push a false theory that Ukraine meddled in the 2016 election.
She said the president had instead listened to the views of his personal lawyer, Rudy Giuliani.
Fiona Hill called the claims about Ukraine a “fictional narrative”.
The inquiry is assessing if President Trump withheld aid to pressure Ukraine to investigate a political rival.
President Trump denies any wrongdoing.
According to a discredited theory, it was Ukrainians or individuals with Ukrainian connections who interfered in the 2016 vote, rather than Russia.
In a phone call with the Ukrainian president, President Trump urged him to look into the claims as well as open an investigation into Joe Biden, one of the main Democratic presidential candidates.
November 21 is fifth and last scheduled day of public hearings by the House Intelligence Committee.
In her opening statement, Fiona Hill – the former top Russia experts to the White House – accused other Republicans of sowing doubt about Russian interference in the 2016 elections.
She said: “Based on questions and statements I have heard, some of you on this committee appear to believe that Russia and its security services did not conduct a campaign against our country – and that perhaps, somehow, for some reason, Ukraine did.”
Fiona Hill urged lawmakers not to promote “politically driven falsehoods” that cast doubt on Russia’s interference in US elections.
“This is a fictional narrative that has been perpetrated and propagated by the Russian security services themselves,” she said.
During Fiona Hill’s testimony, Democratic lawyer Daniel Goldman asked her: “So is it your understanding then that President Trump disregarded the advice of his senior officials about this theory and instead listened to Rudy Giuliani’s views?”
“That appears to be the case, yes,” she replied.
In her later testimony, Fiona Hill warned that Rudy Giuliani had been making “explosive” and “incendiary” claims about Ukraine.
She said: “He was clearly pushing forward issues and ideas that would, you know, probably come back to haunt us.
“I think that’s where we are today.”
Fiona Hill testified that she had a couple of “testy encounters” with Gordon Sondland – the US ambassador to the EU who testified on November 20 – over Ukraine, because the ambassador did not keep her informed of “all the meetings he was having”.
US ambassador to Ukraine David Holmes also testified at November 21 hearing.
In his opening statement, David Holmes said that his work at the embassy in Kiev became overshadowed in 2019 by the actions of Rudy Giuliani.
He said: “I became aware that Mr. Giuliani, a private lawyer, was taking a direct role in Ukrainian diplomacy.”
David Holmes added that he was “shocked” on July 18 when an official from the White House Office of Management and Budget (OMB) announced that military aid to Ukraine was being withheld.