Donald Trump's former adviser Michael Flynn under investigation from Pentagon amid FBI probe

The investigation concerns payments of more than $33,000 that Mr Flynn received from Russian state-backed television network Russia Today in 2015. As a retired Army officer, Mr Flynn was obligated to request permission from the Department of Defense and State Department before receiving payments from foreign governments, members of the Oversight Committee allege.

The Department of Defense told The Independent that they initiated their investigation of Mr Flynn on 4 April – weeks before the Oversight Committee first took their accusations public.

Mr Flynn’s lawyer would not answer questions about whether Mr Flynn had properly disclosed the payments.

The Oversight Committee also released documents on Wednesday showing that the Pentagon warned Mr Flynn not to take foreign government payments without approval. A letter sent by the DIA to Mr Flynn upon his resignation in 2014 explicitly states that “foreign compensation requires advance approval.”

“The Emoluments Clause of the U.S. Constitution ... prohibits receipt of consulting fees, gifts, travel expenses, honoraria, or salary by all retired military personnel, officer and enlisted, regular and reserve, from a foreign government unless congressional consent is first obtained,” the letter reads.

The letter instructs Mr Flynn to “obtain advance approval from the Army” before receiving any such payments