WASHINGTON - OCTOBER 01: Rep. Alan Grayson (D-FL) listens to Federal Reserve Board Chairman Ben Bernanke testify during a House Financial Services Committee hearing on Capitol Hill on October 1, 2009 in Washington, DC. The committee is hearing testimony on the Federal Reserves financial regulatory reform proposals. (Photo by Mark Wilson/Getty Images)

Rep. Alan Grayson (D-Fla.) doesn’t trust that former NSA director Keith Alexander is reportedly being paid $600,000 a month by the largest banking trade groups in the country merely for his advice on cyber security issues.

Alexander, who has repeatedly warned of the financial industry's vulnerability to state-sponsored cyber attacks, recently entered negotiations with the Security Industries and Financial Markets Association (SIFMA), Consumer Bankers Association and the Financial Services Roundtable as a cyber-consultant. He initially set his service fee at $1 million a month, according to Bloomberg.

“It would be devastating if one of our major banks was hit, because they’re so interconnected,” Alexander, who retired from the NSA in March, told Bloomberg last week.

Alexander's resignation was announced in October 2013, amid revelations of the agency's controversial surveillance programs leaked by former intelligence contractor Edward Snowden.

In a letter to the three groups Wednesday, Grayson accused the former head of U.S. Cyber Command of disclosing classified information obtained while serving at the NSA for personal gain.

“Disclosing or misusing classified information for profit is, as Mr. Alexander well knows, a felony. I question how Mr. Alexander can provide any of the services he is offering unless he discloses or misuses classified information, including extremely sensitive sources and methods,” he wrote SIFMA. “Without the classified information that he acquired in his former position, he literally would have nothing to offer to you.”

Grayson, a longtime critic of the NSA, also cited security expert Bruce Schneier, who initially flagged the costly fee as a potential indication of classified disclosures.

“Think of how much actual security they could buy with that $600K a month,” Schneier wrote on Tuesday. “Unless he's giving them classified information.”

Grayson asked all three organizations to "send me all information related to your negotiations with Mr. Alexander, so that Congress can verify whether or not he is selling military and cybersecurity secrets to the financial services industry for personal gain."

Last month, the House Science and Technology Committee passed Grayson’s Internet security amendment, marking the first time any body of Congress approved legislation restricting NSA powers.