In a surprising move, former District Attorney Lynne M. Abraham and powerhouse defense attorney Richard Sprague jointly filed a lawsuit in Common Pleas Court on Monday afternoon seeking to have indicted District Attorney Seth Williams removed from office.

The filing added a new chapter to the contentious personal history of Williams and Abraham, and another layer to Williams' mounting legal woes.

Williams agreed last week to a temporary suspension of his law license in light of the federal bribery and corruption charges that he faces. But he has refused to resign, choosing instead to adopt an administrative role in the District Attorney's Office — a stance that calls to mind his onetime political nemesis, former Pennsylvania Attorney General Kathleen G. Kane.

Kane's ability to remain in office for nearly a year after her law license was suspended in the wake of a 2015 indictment could prove helpful to Williams.

In their lawsuit, Abraham and Sprague argue that state law prohibits Williams from continuing as the city's top prosecutor. Since Williams "is no longer licensed to practice law in the Commonwealth of Pennsylvania," the lawsuit reads, "he does not meet the statutorily required qualifications to occupy the office of the Philadelphia District Attorney. …"

Abraham and Sprague are calling on the court to immediately "extinguish" Williams' attempt to stay in the District Attorney's Office. The lawsuit alleges that he has betrayed the public's trust, and will "undoubtedly" use his $175,572 salary to pay for his legal defense.

Williams' attorney, Thomas Burke, did not respond to a request for comment. A spokesman for the District Attorney's Office also declined to comment.

"He should do the right thing," Abraham said Monday night, "and allow the office to get out from under the cloud caused by his troubles, which will only continue."

In recent interviews with the Inquirer and Daily News, three experts — lawyers Adam Bonin and Gregory Harvey, and law professor Bruce Ledewitz — all said they did not think Williams' suspended license would bar him from staying on the job.

Kane's fate proved to be something of a template; the state Supreme Court voted unanimously to suspend her license after she was indicted on perjury charges, but then-Chief Justice Thomas Saylor said Kane was still technically a member of the bar, and thus could remain in office. She shifted over to an administrative role, and resigned only after being found guilty of nine criminal charges in August 2016.

But Kane's ability to hang onto her title did not deter Abraham and Sprague from taking action.

"We're not aware of instances where private individuals have taken these steps, but that's not going to dissuade us in any way," said Sprague & Sprague attorney Peter Greiner, who filed the lawsuit on behalf of Abraham and Sprague.

"We both have great passion for the office, and the kind of office we know it can and should be," she said. "You can disagree with their decisions, but a district attorney has to be above all ethical — true north in their actions and deeds."

Williams joined the District Attorney's Office in 1992 while Abraham was the city's top prosecutor. He gradually rose through the ranks, but the two sometimes clashed.

Abraham recently told the Inquirer and Daily News that she frequently admonished Williams for partying too much while he was a young prosecutor. She also questioned his work ethic.

Williams left the District Attorney's Office in 2003, and sent Abraham a letter in which he referred to her as "Mama Lynne." He invited her to his farewell party, where he shockingly announced that he intended to run against her in the Democratic primary in 2005.

Williams lost that race. But Abraham decided against running for another term in 2009, which cleared a path for Williams, who promised to usher in a host of procedural and policy reforms. The federal indictment, however, portrays Williams as a pol who eagerly sought gifts and trips from several benefactors.