Flynn, who advised President Donald Trump's election campaign but was fired 22 days into the new adminstration, is under investigation.
Flynn, who advised President Donald Trump's election campaign but was fired 22 days into the new adminstration, is under investigation for misreporting his contacts with Russian officials and his alleged lobbying activities for Turkey while involved in the campaign.
A new website for the Michael T. Flynn Legal Defense Fund called his lawyer bills "tremendous."
"The costs of legal representation associated with responding to the multiple investigations that have arisen in the wake of the 2016 election place a great burden on Mike and his family," the site said.
"Any support provided is greatly appreciated."
Flynn faces probes in Congress, from Robert Mueller, the Justice Department's independent prosecutor into Russian interference, and in the Defense Department, where Flynn formerly served as head of the Defense Intelligence Agency.
He has not been charged with anything.
But the investigations focus on several areas: his repeated discussions of US policy with Russian officials before and after Trump's shock election victory in November 2016; accepting hundreds of thousands of dollars to lobby for Turkey while advising Trump; being paid $33,750 by Russian TV RT to appear at a Moscow event; and his efforts to bring together Russia, the United States and Saudi Arabia in a deal for nuclear plants in the Middle East.
Potential charges include not reporting his business meetings, travels and payments as he was obligated to do as a former senior US military official.
Flynn's defense fund could potentially benefit from a change in the law to allow anonymous lobbyist and business donations to White House officials needing help with their legal defense, according to a Politico report last week.
Trump, his son Donald Trump Jr., son-in-law Jared Kushner, and several other current and former advisors have all retained lawyers to deal with the investigations, with lawyers fees for some topping $1,000 and hour, according to reports.