A "disturbing" email put Jonathan Silver, former head of the Department of Energy's green loan program, in the hot seat even before the questioning began Tuesday at a House Oversight and Government Reform Committee hearing.

Committee Chairman Rep. Darrell Issa, R-Calif., read an email from an employee at Dickstein Shapiro, a major D.C.-based law and lobbying firm, requesting that the committee not question Silver.

"In your opening statement, you said you wanted to be transparent," Issa said to Silver. "I have in my possession a disturbing email that comes from an individual apparently working at Dickstein Shapiro that actually asks a member of this committee not to ask questions of you. Are you familiar with this? Can you consult with your counsel?"

"I'm sorry, sir, I am not at all familiar with this," Silver said.

"The question of whether we refer this to the Bar Association, whether in fact it's an interference with Congress -- which I find it to be -- and the like, that will need to be resolved with the ranking member and myself after this hearing," Issa said.

"But we have had a long history. Dickstein Shapiro Morin has represented a lot of individuals here. This one crosses the line."

Rep. Elijah Cummings, the Maryland Democrat who is ranking minority member of the committee, also expressed concern about the email, saying, "I hope this is not what it appears to be. It would really be out of bounds."

Rep. Jim Jordan, R-Ohio, described the email as adding insult to injury later in the hearing after questioning Silver about emails he sent while working at the energy department, telling employees not to mix government and personal emails because doing so would make the personal emails "subpoenable."

Jordan also pointed to what he described as apparent collusion between government officials and employees at BrightSource Energy, which received a $1.6 billion loan through the green loan program Silver oversaw.

"Finally, we have your lobbyist saying to the committee just a couple days ago, 'Don't direct any questions to Mr. Silver,'" Jordan said. "You can mislead a member of Congress, you can help your friends, you can lose billions of taxpayer dollars and still have the gall for your lobbyist to ask members of Congress not to ask you any questions. Do you think taxpayers might take offense to that whole scenario?"

Emails released in May 2012 show Silver helped edit an email from BrightSource CEO John Woolard intended for then-White House Chief of Staff Bill Daley, which was never sent, over concerns it was not appropriate.

Silver called the allegations a "mischaracterization." He told Jordan the letter was drafted after the energy company's loan had been approved. He claimed he was not seeking to help BrightSource to gain that approval.