KYIV, Nov. 4 - Ukraine plans to fire the prosecutor who led investigations into the firm where Joe Biden’s son served on the board, a central figure in the activity at the heart of impeachment proceedings against U.S. President Donald Trump, a source told Reuters.

Trump’s personal lawyer Rudy Giuliani has acknowledged meeting the prosecutor, Kostiantyn Kulyk, to discuss accusations against the Bidens.

The decision to sideline someone who played an important role in Giuliani’s efforts to find out damaging information about the Bidens comes as Ukraine has tried to avoid getting drawn into a partisan fight in Washington.

Trump’s Democratic opponents have launched impeachment proceedings, arguing that Trump abused his power by pressing Ukraine to investigate the Bidens to hurt the former vice president, front-runner to challenge him in the 2020 election.

The source said a decision had been taken to fire Kulyk for failing to show up for an exam that all employees of the General Prosecutor’s Office have been ordered to pass to keep their jobs during a clean-up of the prosecution service.

Prosecutor General Ruslan Ryaboshapka has already fired more than 400 prosecutors, or around a third of all staff.

Some prosecutors have told Reuters that many of those sacked had refused to sit the exam in protest at what they see as a purge designed to cement new President Volodymyr Zelenskiy’s political control of the service.

Zelenskiy has said the overhaul is essential because the office is widely distrusted by Ukrainians and had been seen as a political tool for the well-connected to punish their enemies.

Trump discussed investigating the Bidens during a July 25 phone call with Zelenskiy. Trump’s Democratic opponents have launched impeachment proceedings, arguing that Trump abused power to press Ukraine to hurt a political foe. Trump calls the investigation a witch hunt and denies wrongdoing.

Reuters was unable to reach Kulyk for comment.

Kulyk did not show up for the mandatory exam, which was imposed last month, the source said.

He also did not file an official justification for missing it, as other prosecutors have done, and will consequently be dismissed, the source said. His dismissal will take place by Dec. 31, if not earlier.

Earlier this year, Kulyk compiled a seven-page dossier on the business activities of Hunter Biden in Ukraine, two sources told Reuters. (rt/ez)