Robert Mueller has proof to charge Micheal Flynn

Mr Mueller is increasing pressure on Mr Flynn following his indictment of former Trump campaign manager Paul Manafort, NBC said.

NBC also reports that Flynn's son could be under investigation for work that he did under his father's lobbying firm.

White House officials have previously stressed that those charged to date were campaign officials who were not brought into government by Mr Trump.

Mr Mueller's team are also said to be looking at whether the former National Security Adviser attempted to have Fethullah Gullen, an elderly Muslim cleric, extradited from the USA to Turkey in exchange for millions of dollars.

Sources "familiar with the investigation" say Flynn, who was sacked after just 24 days, and his son could be implicated in the probe into Russia's intervention in last year's election, according to NBC News.

If charged, Flynn would become the first member of Trump's administration to face prosecution in the growing, wide-ranging investigation into whether the president's campaign team colluded with Russian Federation to damage the reputation of Hillary Clinton. A spokesman for the Special Counsel's Office declined Bustle's request for comment. "I've seen documentation, classified and not, of Michael Flynn's activities and charges from Mueller wouldn't remotely surprise me, but we're still talking about someone who had access to our nation's vital secrets while working in the White House".

Mr Manafort and his business partner, Rick Gates, were charged with 12 offences, including money laundering and conspiracy against the US. Sanders had also said President Donald Trump "has confidence they're going to close this up soon".

After Trump fired James Comey in May, the former FBI director testified that the president had suggested to him that the bureau drop a potential criminal investigation into Flynn.

Another Trump campaign aide, George Papadopoulos, pleaded guilty to lying to FBI investigators.

  • Joey Payne