Donald Trump on Wednesday pardoned his former national security adviser Michael Flynn, who had admitted to lying to the FBI in an investigation into Russian interference in the 2016 presidential election. Flynn lasted only 24 days as Mr Trump's first national security adviser before he was fired by the president in early 2017, as controversy broke out over his interactions with the Russian ambassador at that time, Sergey Kislyak. "It is my great honour to announce that Gen Michael Flynn has been granted a full pardon," Mr Trump wrote on Twitter. "Congratulations to Gen Flynn and his wonderful family. I know you will now have a truly fantastic Thanksgiving." Flynn pleaded guilty in 2017 to lying to the FBI about contacts he had with Mr Kislyak leading up to the president's inauguration in January of that year. He since sought to withdraw the plea, saying that prosecutors breached his rights and duped him into a plea agreement. His sentencing has been deferred several times. This is among the highest-profile pardons granted by Mr Trump since he came to power. This month he lost the presidential election to former vice president Joe Biden and made unsubstantiated claims of electoral fraud. Flynn was one of several former Trump aides to plead guilty or be convicted in former special counsel Robert Mueller’s investigation into Russia's interference, which Moscow still denies. Mr Trump in March said he was strongly considering a full pardon for Flynn. He claimed the FBI and Justice Department had "destroyed" Flynn's life and that of his family. Mr Trump said an unspecified, unsubstantiated report claimed records related to Flynn had been lost. Flynn was supposed to co-operate with the government as part of his plea deal, but he later switched lawyers and tactics. He said prosecutors in the case tricked him into lying about his December 2016 conversations with Mr Kislyak. Federal prosecutors had asked the judge in January to sentence Flynn to up to six months in prison, saying in a court filing that "the defendant has not learnt his lesson". "He has behaved as though the law does not apply to him and as if there are no consequences for his actions," they said.