WASHINGTON — The Republican leaders of a House committee who have been in a bitter partisan battle with Democrats are enmeshed in a new fight with one of the committee’s former staff members.

A former investigator for the Republicans on the House Select Committee on Benghazi plans to file a complaint in federal court next month alleging that he was fired unlawfully in part because his superiors opposed his efforts to conduct a comprehensive investigation into the 2012 attack on the American diplomatic mission in the Libyan city. Instead, they focused primarily on the role of the State Department and former Secretary of State Hillary Rodham Clinton, he said.

The former investigator, Bradley F. Podliska, a major in the Air Force Reserve who is on active duty in Germany, also claims that the committee’s majority staff retaliated against him for taking leave for several weeks to go on active duty. If true, the retaliation would violate the federal Uniformed Services Employment and Reemployment Rights Act of 1994, which Major Podliska plans to invoke in his complaint, according to a draft that was made available to The New York Times.

The committee firmly disputed Major Podliska’s allegations, saying Saturday that he had been “terminated for cause.”