KIEV (Reuters) - Sweeping changes to Ukraine’s top law enforcement agency ordered by President Volodymyr Zelenskiy are set to derail a series of long-running criminal investigations, including two related to U.S. President Donald Trump’s former campaign chairman, Paul Manafort, three current and former Ukrainian prosecutors told Reuters.

The reorganization, which includes fresh leadership for the agency and mandatory skills testing for prosecutors, represents an upheaval of Ukraine’s General Prosecutor’s Office (GPO), one of the most powerful bodies in the country, and one that has long been the target of criticism.

Zelenskiy, who came to power in May, has said the makeover is essential because the office is widely distrusted by Ukrainians and has been seen as a political tool for the well-connected to punish their enemies.

The overhaul, which began in October, comes amid widespread scrutiny of the agency following efforts by Trump and his personal attorney, Rudy Giuliani, to get Ukraine to open an investigation into the Republican president’s political rival - Democratic presidential candidate Joe Biden - and his son Hunter, who served on the board of a Ukrainian gas company.

Plans to shake up the GPO played a role in a July 25 phone call between Zelenskiy and Trump that is now at the heart of the impeachment inquiry into the U.S. president. On that call, Zelenskiy told Trump he was installing a new head at the agency who would be “100% my person, my candidate” and who “will look into the situation” regarding the Bidens.

New Prosecutor General Ruslan Ryaboshapka took office at the end of August. Under his leadership, the GPO is preparing to transfer all existing investigations to other law enforcement agencies, a process the GPO told Reuters would begin Nov. 20.

Ryaboshapka, who previously headed an anti-corruption agency and briefly served as Zelenskiy’s deputy chief of staff, also has imposed a written legal exam for all the GPO’s prosecutors, a move many of those staffers view as insulting and an unfair test of their skills and experience. More than 200 have already been fired for refusing to take the exam, according to the prosecutor’s office.

During a press conference in October, Zelenskiy said what he meant in his comments to Trump was that Ryaboshapka would be an honest prosecutor. Ryaboshapka declined to be interviewed by Reuters and has not responded directly to questions sent by Reuters about the criticism of his reforms. But his office defended them and the exam process. “The purpose of the reform is to create a renewed, professional, efficient prosecutor’s office that will be trusted by the public,” it said in a statement on Oct. 25.

Among those who have been fired are 13 prosecutors from the Special Investigations Unit, which was overseeing corruption cases from the period of former President Viktor Yanukovich. Manafort, who worked as a political consultant in Ukraine for years, was implicated in two of those probes, one linked to a dossier of off-the-books payments made by a Ukrainian political party, and another looking at the alleged illicit use of state funds by Yanukovich’s government.

Manafort’s attorney did not respond to requests for comment, but Manafort previously has maintained his innocence.

Serhii Horbatiuk, the former head of the Special Investigations Unit, who was fired for refusing to take the new test, said he believed Zelenskiy’s overhaul was aimed at concentrating power in the hands of loyalists who could exercise more control over sensitive cases, including the probes linked to Manafort.

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“This entire reform is being done in order to take control of the General Prosecutor’s Office... and have the guarantee that there will be no dissent,” Horbatiuk said in an interview with Reuters conducted in his office on Oct. 22, the day before he was fired.

He and two other prosecutors in his former unit said the transfer of long-running investigations out of the GPO, along with the dismissal of seasoned investigators working on those cases, would result in a massive backlog – and the de facto demise - of the probes.

“In the fog of this reform you can create such a pile of cases…which will lead to an absence of results,” Horbatiuk said.

Those fears are overblown, according to Andriy Smirnov, the deputy chief of staff of Zelenskiy’s administration responsible for handling judicial reform. He said no critical knowledge would be lost if the cases moved to other departments, including the probes related to Manafort.

“All of this is easy and happens quickly. With no harm to the investigation,” Smirnov told Reuters. “The problem being described to you does not exist.”

Smirnov said the overhaul was in no way designed to allow the government to influence politically sensitive cases. He described the allegations made by Horbatiuk and two other senior members of his former unit as a “paranoid” response to new leadership.

In comments to journalists on Oct. 30, Ryaboshapka described the work of Horbatiuk and his team as “ineffective”.

‘BLACK LEDGER’ CASE

Three members of the Special Investigations Unit told Reuters the loss of key personnel and reshuffling of responsibilities would effectively sabotage five years’ worth of investigations into alleged corruption during the pro-Kremlin presidency of Yanukovich, who was in office from 2010 until he was driven from power in a popular revolt in 2014. Manafort worked as a consultant for Yanukovich’s political party for over a decade.

“At least 50% of the information… is in the investigator’s head, it doesn’t fit into the official paperwork,” said Andriy Rodionov, a senior investigator in the unit who is still on staff after passing the mandatory exam. “Any handing over of these cases is an automatic burial of them.”

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Manafort was Trump’s campaign chairman from May to August of 2016. He stepped down after a Ukrainian lawmaker divulged details contained in a so-called “black ledger” of alleged off-the-books payments made by Yanukovich’s Party of the Regions. Manafort, who earned millions for his consultancy work in Ukraine, was among the recipients listed in the ledger, which was corroborated at the time by anti-corruption investigators and which prosecutors told Reuters has long been the subject of a GPO probe.

Following Special Counsel Robert Mueller’s investigation into Russian interference in the 2016 U.S. election, Manafort was convicted of bank fraud and filing false tax returns and sentenced to 7.5 years in U.S. prison. In building their case against Manafort, U.S prosecutors accused him of concealing the payments he received from Ukraine.

In Ukraine, senior investigator Rodionov said prosecutorial firepower was sputtering when it came to the probes involving Manafort. He said he has already lost three members of his team as part of Zelenskiy’s restructuring; two refused to take the test and another failed it, he said. Overall, the Special Investigations Unit has lost around a third of its staff, Rodionov said, with the number likely to rise as more prosecutors either refuse to participate in further rounds of assessment or fail to pass them.

Giuliani has called the black ledger a fraudulent document used to unfairly malign Manafort and damage Trump. He has urged Ukraine to investigate whether Ukrainian officials conspired to meddle in the 2016 U.S. presidential election on behalf of Democrat Hillary Clinton, a conspiracy theory that has been widely debunked.

Giuliani did not respond to requests to comment for this story. He told Reuters in a recent interview that “some” Ukrainians say the black ledger is forged. Earlier this year he said that Manafort had communicated to him through an attorney that the ledger’s “entries about me are false.”

Rodionov said his team had been “within weeks” of announcing official suspects in the second probe linked to Manafort, which involves allegations that Yanukovich’s administration illegally used state funds to pay a prominent New York law firm to write a report justifying the imprisonment of one of Yanukovich’s political rivals. Manafort helped the Ukrainian government commission that report, and he promoted its conclusions to reporters and others in the United States.

“We were ready…to formally announce indictments of both Ukrainian and American citizens,” Rodionov said. “I spent three years trying to put it all together and now they will crumple it up and stuff it all in a box and hand the box away.”

A quiet end to Ukraine’s investigations into Manafort would likely play well in the White House. Trump and his backers have worked for years to discredit Mueller’s Russia investigation, and Trump has previously talked about pardoning Manafort.

A recent survey by Rating Group Ukraine, an independent polling firm, found that almost two-thirds of Ukrainians don’t trust the GPO. Critics say that, under previous presidents, the office was used to go after political opponents, squeeze businesses or shield corrupt officials.

Since Ukraine gained independence from the Soviet Union in 1991, the country has had more than 20 prosecutors general. Not one has completed the designated five-year term, which was extended to six years in 2017.

Yuriy Bezshastniy, another Special Investigations Unit prosecutor who was fired for refusing to take the law exam, said the reorganization was harming the ability of the nation to hold powerful wrongdoers accountable. He said he found it difficult to understand why the reforms had been introduced or who had come up with them.

“I’m seeing all sorts of nonsense,” he said. “Was it politicians or businessmen or clowns or lawyers? What’s going on is an absolute nightmare,” said Bezshastniy, who had served in the prosecutor’s office since 2001.

Asked what would happen to Yanukovich-era cases, he replied: “It’s an end to them. They’re killing two birds with one stone -- kicking out people who were actually doing something... and messing up all the cases with one stroke of a pen.”