House Select Committee on Benghazi Chairman Trey Gowdy (R-S.C.) walks to a hearing room on Capitol Hill on Sept. 4. (Cliff Owen/AP)

A House investigative committee is requiring an in-person appearance Thursday by the former State Department staffer who worked on Hillary Rodham Clinton’s private e-mail server and has invoked his Fifth Amendment rights to refuse to answer lawmakers’ questions.

The decision by the House Select Committee on Benghazi to require the presence of former staffer Bryan Pagliano prompted a stern letter Wednesday from Pagliano’s lawyer, who accused the panel and its chairman, Rep. Trey Gowdy (R-S.C.), of engaging in political theater and abusing its subpoena power.

“Forcing Mr. Pagliano to appear, restate the advice of his counsel, and decline to respond to questions can only be intended to intimidate our client, cause him personal embarrassment, and foster further political controversy,” wrote Mark MacDougall, Pagliano’s attorney, in a letter obtained by The Washington Post.

Gowdy said in a letter responding to MacDougall that he “wants to state expressly and unequivocally” that he has no plans to intimidate or harass Pagliano. Rather, Gowdy wrote, he believes the committee can appropriately summon Pagliano for lots of reason, among them to assess whether he may change his mind about talking and whether to talk to him in a closed executive session.

“Nothing could be further from the truth,” he wrote of MacDougall’s accusation of the committee harassing Pagliano. “Our intention is to explore topics relevant to the Committee’s jurisdiction.”

Still, the back and forth underscored the extent to which the Clinton e-mail controversy has emerged as a partisan divide on the panel, which was created to probe the 2012 attacks on U.S. diplomatic posts in Libya.

Rep. Elijah E. Cummings (D-Md.), the ranking Democrat on the committee, said in a statement he agreed with the criticism by Pagliano’s attorney of the subpoena and said that forcing witnesses to appear in person to assert their Fifth Amendment rights is designed “just for a photo op.” Cummings said the confrontation showed the GOP-led House committee was more interested in damaging Clinton’s bid for the White House.

“Mr. Pagliano’s testimony has nothing to do with the Benghazi attacks and everything to do with Republicans’ insatiable desire to derail Secretary Clinton’s presidential bid,” Cummings said.

Clinton’s former chief of staff, Cheryl D. Mills, as well as Jake Sullivan, her former deputy chief of staff, each testified for hours at closed meetings of the committee last week. Clinton is scheduled to testify in open session Oct. 22.

Pagliano, who worked as a computer aide on Clinton’s 2008 presidential campaign, helped manage her server at that time. When Clinton became secretary of state, Pagliano got a job as a State Department IT staffer. He was also paid personally by the Clintons to continue managing the private server from 2009 to 2013.

In his letter Wednesday, MacDougall wrote that the Benghazi committee’s likely questions for Pagliano — about his knowledge of Clinton’s decision to exclusively use a private e-mail while secretary of state — are far afield from “the stated purpose of the Select Committee to investigate the events surrounding the 2012 terrorist attack in Benghazi.”

He added that the Justice Department’s guidelines for prosecutors and the D.C. Bar rules that cover congressional attorneys generally discourage forcing a witness to testify when the witness has made clear they will assert their Fifth Amendment rights and not answer questions.

Legal experts on congressional investigations said the Benghazi committee is likely not engaging in any ethical violation. There is nothing unusual about Congress forcing reluctant witnesses to appear for questioning, they said, but they added that the practice is generally frowned upon.

Congress has broad powers to investigate, the experts stressed. The committee can argue that it is not trying to harass Pagliano but hopes he will change his mind or wants to make clear to the public that witnesses are not cooperating.

“In general I don’t condone that practice,” white collar lawyer and former Whitewater prosecutor Solomon Wisenberg said of calling a witness like Pagliano. “If a person has made it clear they are going to invoke the Fifth Amendment, why summon them?”

Also Wednesday, Pagliano’s lawyer wrote to the Senate Homeland Security and Senate Judiciary Committees to decline their request to talk with their staff about what his client may have known about setting up Clinton’s e-mail system while she was secretary of state. MacDougall wrote that if he talked to the committees, he could jeopardize Pagliano’s constitutional right to decline to answer questions of other committees.

“Any… disclosure by Mr. Pagliano – or his lawyers acting on his behalf – … creates the very practical risk that our client will later be said to have waived his constitutional protections,” MacDougall wrote. “We cannot set the stage for any such episode by engaging in the kind of discussion with the Committees’ staff as suggested in your letter.”