US President Donald Trump asked FBI chief James Comey to end an inquiry into links between his ex-national security adviser and Russia, US media reports.
According to a New York Times article, Mr Comey wrote a memo following a meeting with the president on 14 February that revealed Mr Trump asked him to close an investigation into Mr Flynn's actions.
He reportedly shared the memo with top FBI associates.
"I hope you can see your way clear to letting this go, to letting Flynn go," the president told Mr Comey, according to the memo. "He is a good guy".
Mr Comey did not respond to his request, according to the memo, but responded: "I agree he is a good guy."
It comes a week after Mr Trump fired Mr Comey, which he said was over the handling of the FBI investigation into Hillary Clinton's use of a private email server while at the State Department.
The White House has denied the report in a statement.
"While the president has repeatedly expressed his view that General Flynn is a decent man who served and protected our country, the president has never asked Mr Comey or anyone else to end any investigation, including any investigation involving General Flynn," the statement read.
In response to the report, a White House official also pointed out that acting FBI director Andrew McCabe testified last week that there "has been no effort to impede our investigation to date".
Mr Flynn resigned as White House national security adviser after just 23 days on the job over revelations that he discussed lifting sanctions on Moscow with Russian ambassador, Sergei Kislyak, before Mr Trump was sworn in.
His departure in February came months after suspicions were raised among intelligence officials.
It is illegal for private citizens to conduct US diplomacy.
Since Mr Flynn stepped down, the Pentagon has launched an investigation into whether he failed to disclose payments from Russian and Turkish lobbyists for speeches and consulting work.
He has also registered with the US government as a "foreign agent" due to his work for the Turkish government.
Former acting Attorney General Sally Yates, who was fired by Mr Trump in January for refusing to uphold his travel ban, told a Senate panel earlier this month that she had warned the White House about Mr Flynn.
Ms Yates said Mr Flynn's actions created "a situation where the national security adviser essentially could be blackmailed by Russians".
Mr Flynn's Russian ties are under investigation by the FBI and and the House and Senate Intelligence Committees, as part of wider inquiries into claims Moscow sought to tip the election in favour of Mr Trump.
Contacts between Russia and members of the president's campaign team are also under scrutiny.
Mr Comey's sacking on 9 May fuelled claims that Mr Trump may have been trying to cover up his associates' Moscow ties.