The US Justice Department has said it is dropping the criminal case against President Donald Trump’s first national security adviser, Michael Flynn.

It is abandoning the prosecution that became a rallying cry for President Trump and his supporters in attacking the FBI’s Russia investigation.

The move is a stunning reversal for one of the signature cases brought by special counsel Robert Mueller.

Attorney General William Barr  (Alex Brandon/AP)
Attorney General William Barr (Alex Brandon/AP)

It comes even though prosecutors for the last three years had maintained that Mr Flynn had lied to the FBI about his conversations with the Russian ambassador in a January 2017 interview.

Mr Flynn himself admitted as much, and became a key cooperator for Mr Mueller as he investigated ties between Russia and the 2016 Trump campaign.

In court documents being filed Thursday, the Justice Department said it is dropping the case “after a considered review of all the facts and circumstances of this case, including newly discovered and disclosed information”.

The Justice Department said it had concluded that Mr Flynn’s interview by the FBI was “untethered to, and unjustified by, the FBI’s counterintelligence investigation into Mr Flynn” and that the interview on January 24, 2017 was “conducted without any legitimate investigative basis”.

The US attorney reviewing the Flynn case, Jeff Jensen, recommended the move to Attorney General William Barr last week and formalised the recommendation in a document this week.

“Through the course of my review of General Flynn’s case, I concluded the proper and just course was to dismiss the case,” Mr Jensen said in a statement.

“I briefed Attorney General Barr on my findings, advised him on these conclusions, and he agreed.”

The decision is certain to be embraced by President Trump, who has relentlessly tweeted about the case and last week pronounced Mr Flynn “exonerated”, and will energise supporters who have taken up the retired Army lieutenant general as something of a cause celebre.

But it may also add to Democratic concerns that Attorney General William Barr is excessively loyal to the president, and could be a distraction for a Justice Department that for months has sought to focus on crimes arising from the coronavirus.