Michael Flynn 'could be blackmailed by Russian officials'
Video report by ITV News Washington Correspondent Robert Moore
A former acting US attorney general warned President Trump's administration in January that Michael Flynn "could be blackmailed" by Russian officials.
Mr Flynn, a retired general who advised Donald's Trump's election campaign, was sacked in February after it emerged he concealed the nature of his contact with Russia's US ambassador, Sergei Kislyak, ahead of Trump's inauguration.
He emerged as a central figure into possible collusion between Trump's campaign and Russia, and was accused of relaying misleading information to vice president Mike Pence.
Sally Yates, who was originally appointed by the Obama administration, told a Senate Judiciary subcommittee that she felt Pence "was entitled to know" he was relaying incorrect information about Flynn to the American public.
Yates - who was sacked by President Trump in January after refusing to defend his executive order on implementing travel restrictions for seven Muslim-majority countries - said: "I had two in-person meetings and one phone call with the White House Counsel about Mr Flynn.
"The underlying conduct that General Flynn had engaged in was problematic.. we were concerned the American people had been misled about his underlying conduct.
"The Russians also knew what General Flynn had done, and the Russians also knew that General Flynn had misled the vice president and others.
"This was a problem because not only do we believe the Russians knew this, but that they likely had proof of this information."
She added: "That created a compromise situation - a situation where the national security advisor essentially could be blackmailed by the Russians.
"Logic would tell you that you don't want the national security adviser to be in a position where the Russians have leverage over him."
Donald Trump waited more than two weeks after the warning to fire Michael Flynn.
Earlier, it emerged that former US President Barack Obama had also made it clear to president-elect Donald Trump that he did not support his decision to appoint Michael Flynn as national security adviser.
During their one-hour meeting at the Oval Office on November 10 - two days after the Republican's surprise US election win - Mr Obama "made it known that he wasn't exactly a fan of General Flynn", White House spokesman Sean Spicer said.
Mr Flynn was a former aid to Barack Obama but was sacked as head of the Defence Intelligence Agency in 2014.
Hours before Monday's Senate hearing, Trump insinuated that Yates had leaked information on Flynn to the media.