US President Donald Trump has pardoned his former national security adviser Michael Flynn who pleaded guilty to lying to the FBI during the investigation into Russian meddling in the 2016 presidential election.

Using executive powers still available until he leaves office in January, Mr Trump announced the pardon on Twitter, wishing the former military general a “truly fantastic Thanksgiving”.

Tweet from @realDonaldTrump

House Intelligence Committee Chair Adam Schiff said the pardon wasn’t a surprise but was nonetheless “crooked”.

“Flynn pled guilty to those lies, twice. A pardon by Trump does not erase that truth, no matter how Trump and his allies try to suggest otherwise,” he said.

US House of Representatives Judiciary Committee Chair Jerry Nadler said General Flynn’s pardon was unprincipled.

“The President’s enablers have constructed an elaborate narrative in which Trump and Flynn are victims and the Constitution is subject to the whims of the President,” the Congressman, a Democrat, said in a statement.

“Americans soundly rejected this nonsense when they voted out President Trump.”

General Flynn pleaded guilty in 2017 to lying to the FBI about interactions he had with Russia’s ambassador to the US in the weeks leading up to Mr Trump’s inauguration in January 2017.

He has since sought to withdraw the plea, arguing that prosecutors violated his rights and duped him into a plea agreement. His sentencing has been deferred several times.

General Flynn served as Mr Trump’s first national security adviser. The President fired him in early 2017 – after only 24 days – as a controversy broke over the former general’s contacts with then Russian ambassador Sergei Kislyak.

General Flynn was one of several former Trump aides to plead guilty or be convicted at trial in former special counsel Robert Mueller’s investigation into Moscow’s interference in the 2016 US election to boost Mr Trump’s candidacy.

Russia denied meddling.

Mr Trump said the FBI and Justice Department had “destroyed” General Flynn’s life and that of his family, and cited an unspecified, unsubstantiated report that they had lost records related to General Flynn.

General Flynn was supposed to help co-operate with the government as part of his plea deal.

But he later switched lawyers and tactics, arguing prosecutors in the case had tricked him into lying about his December 2016 conversations with Mr Kislyak.

The US Justice Department has repeatedly denied allegations of prosecutorial misconduct and US District Court Judge Emmet Sullivan rejected all General Flynn’s claims in December 2019.

Federal prosecutors had asked the judge in January to sentence General Flynn to up to six months in prison, arguing in a court filing that “the defendant has not learned his lesson. He has behaved as though the law does not apply to him, and as if there are no consequences for his actions”.

General Flynn also served as head of the Pentagon’s Defence Intelligence Agency. He was forced out in 2014 in part due to his management style and opinions on how to fight Islamist militancy.

He joined the Trump 2016 election campaign and at the Republican National Convention that year led supporters in chants of “lock her up”, in reference to Democratic candidate Hillary Clinton.

In March, Mr Trump said he was strongly considering a full pardon for General Flynn.

A presidential pardon still implies guilt.

A pardon is “granted in recognition of the applicant’s acceptance of responsibility for the crime”, the US Department of Justice says, “and established good conduct for a significant period of time after conviction or completion of sentence. It does not signify innocence”.

It is the highest-profile pardon granted by Mr Trump since he took office.

General Flynn is also the second Trump associate convicted in the Russia probe to be granted clemency by the President.

In July, Mr Trump commuted the sentence of long-time confidant Roger Stone just days before he was to report to prison.

-with agencies