Fiona Hill, President Donald Trump's former adviser on Russia and Europe, on Monday testified White House officials were so alarmed by efforts to press Ukraine into opening an investigation into former Vice President Joe Biden and his son Hunter, they raised their concerns with National Security Council lawyer John Eisenberg, reports The Wall Street Journal.

Hill, a former intelligence officer under ex-President Barack Obama, also raised concerns about Rudy Giuliani's role in U.S. foreign policy toward Ukraine during her nine-hour deposition and viewed the recall of Amb. Marie Yovanovitch from Kiev as an egregious abuse of the system by Trump’s allies who were seeking to remove a perceived obstacle.

The impeachment proceedings center around a July 25 phone call Trump had with Ukraine President Volodymyr Zelenskiy where Trump asked Zelenskiy to launch an investigation into Biden and his son.

Hill, who resigned in August, told lawmakers of a July 10 meeting with Ukrainian officials, then-National Security Adviser John Bolton, and other U.S. officials in which the U.S. Ambassador to the European Union Gordon Sondland raised the issue of such a probe.

Following the meeting, Hill said Bolton told her to speak with Eisenberg over concerns she expressed regarding the sit-down.

Trump has denied wrongdoing and on Twitter on Monday morning, calling the Democrats' inquiry a "total impeachment scam."