Donald Trump's former national security adviser may have broken the law by failing to disclose he had accepted tens of thousands of dollars from Russian organisations in 2015, leaders of a House oversight committee said.
The two leaders of the oversight committee, Republican Jason Chaffetz and Democratic Elijah Cummings, say they've seen no evidence that Michael Flynn, a retired Army lieutenant general, properly disclosed foreign payments.
Among the payments in question was more than $US33,000 ($A43,800) Flynn received in 2015 from the Russia Today television network described by US intelligence officials as a propaganda front for Russia's government.
"That money needs to be recovered," said Chaffetz, chairman of the House Committee on Oversight and Government Reform.
Chaffetz also raised questions about fees Flynn received as part of $US530,000 in consulting work his company performed for a businessman tied to Turkey's government.
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"You simply cannot take money from Russia, Turkey or anybody else," he said.
Cummings said Flynn's failure to formally report the Russian payments on his security clearance paperwork amounted to concealment of the money, which could be prosecuted as a felony.
Chaffetz said Flynn was obliged to request permission from the Defence and State departments about prospective foreign government payments.
"There was nothing in the data to show that General Flynn complied with the law," he said.
Flynn, who headed the military's top intelligence agency, was fired as Trump's national security adviser in February over misleading comments he made to the vice president about his discussions with the Russian ambassador during the transition.
Flynn is among the Trump associates being investigated by Congress and the FBI for possible ties between the Trump campaign and Russia.
