– Michael Flynn, President Donald Trump's former national security adviser, misled Pentagon investigators about his income from companies in Russia and contacts with officials there when he applied for a renewal of his top-secret security clearance last year, according to a letter released Monday by the top Democrat on the House oversight committee.

Flynn, who resigned 24 days into the Trump administration, told investigators in February 2016 that he had received no income from foreign companies and had only "insubstantial contact" with foreign nationals, according to the letter. In fact, Flynn had sat two months earlier beside President Vladimir Putin of Russia at a Moscow gala for RT, the Kremlin-financed television network, which paid Flynn more than $45,000 to attend the event and give a separate speech.

His failure to make those disclosures and his apparent attempt to mislead the Pentagon could put Flynn in further legal jeopardy. Intentionally lying to federal investigators is a felony punishable by up to five years in prison. Separately, he also faces legal questions over failing to properly register as a foreign agent for lobbying he did last year on behalf of Turkey while advising the Trump campaign, which is also a felony.

The House letter, written by Rep. Elijah Cummings of Maryland, was made public hours after Flynn formally rejected a subpoena from senators investigating Russian interference in the 2016 election and chose to instead invoke his right against self-incrimination, a person familiar with his decision said.

Flynn had been ordered by the Senate Intelligence Committee to hand over e-mails and other records related to any dealings with Russians as part of that panel's investigation into Russian election meddling. His decision to invoke his Fifth Amendment right puts him at risk of being held in contempt of Congress, which can also result in a criminal charge.

Flynn's lawyer, Robert Kelner, did not respond to a request for comment.

The controversies surrounding the Trump White House's ties to Russia have overshadowed the early months of the new administration, and Flynn has been at the center of the maelstrom. He is under scrutiny both by congressional committees and by federal law enforcement agencies for his ties to Russia and his business dealings with Turkey.

Lawmakers had previously asserted that Flynn had failed to disclose the income he had received for the Moscow trip to obtain security clearance to work in the White House, but the letter released Monday shows he had misled investigators during a previous attempt to renew his clearance, months before Trump won election.

Cummings quoted directly from the Pentagon report detailing his clearance process. The Pentagon document itself, a "Report of Investigation" from March 2016, was not included with his letter.