When the Trump justice department tapped a US attorney to examine the origins of the FBI inquiry into Russian meddling in the 2016 election, conservatives and many Republicans hoped it would end the idea Donald Trump’s campaign was boosted by Moscow and back his charges that some FBI officials and others had conspired against him.

But instead, as the multi-year investigation winds down, it is ending with accusations that unethical actions by that special counsel – John Durham – and ex-attorney general William Barr “weaponized” the US Department of Justice (DoJ) to help Trump.

Former DoJ officials and top Democrats are voicing strong criticism that Durham and Barr acted improperly in the almost four-year-old inquiry, citing an in-depth New York Times story that added to other evidence the inquiry looked politically driven to placate Trump’s anger at an investigation he deemed a “witch-hunt”.

The Times report provided disturbing new details, for instance, about how a key prosecutor, Nora Dannehy, quit Durham’s team in 2020 over “ethical” concerns, including his close dealings with Barr, and discussions about releasing an unorthodox interim report before the 2020 election that might have helped Trump, but which didn’t come to fruition.

Critics of the Durham inquiry also noted early on that Barr on several occasions, and contrary to longtime DoJ policies, suggested publicly that Durham’s inquiry would yield significant results, which in effect would help validate Trump’s charges that some officials at the FBI and CIA had led a political witch-hunt.

Further, Barr and Durham, in highly unusual public statements early in their investigation, tried to undermine a chief conclusion of a report by the DoJ inspector general, Michael Horowitz, that the Russia investigation was based on sufficient facts to warrant opening the investigation in 2016.

Ex-DoJ officials say the Durham inquiry seemed aimed from the start at boosting Trump’s political fortunes.

“It was clear to people following the Durham investigation as it unfolded that it was highly irregular from the start,” said former deputy AG Donald Ayer who served in the George HW Bush administration “Indeed there’s good reason to believe that its purpose and primary function was to create fodder to advance Trump’s election prospects.”

Critics note that Barr tapped Durham to lead the investigation just a month after special counsel Robert Mueller issued a large report documenting substantial ties between Trump’s campaign and Russia, and concluded that Moscow tried to sway the election to help Trump in “sweeping” and “systematic” ways, a conclusion Barr and Trump worked to downplay.

Despite Trump’s pressures and Durham’s sprawling investigation, including unusual overseas trips with Barr to interview officials in Italy and England about potential flaws in the Russia investigation, the inquiry notched just one minor conviction of a mid-level ex-FBI official for falsifying a document. There were also two embarrassing acquittals.

The Times report revealed too that Durham had uncovered evidence during his Italy trip of possible criminal misconduct by Trump, but it’s unknown what that entailed and how much he pursued that element of the inquiry.

Durham also reportedly spent time investigating a conspiratorial and dubious lead that seemed aimed at connecting an aide to billionaire George Soros, a leading Democratic donor, to the early Russian meddling investigation and the campaign of Trump’s opponent Hillary Clinton.

Besides Nora Dannehy, who left Durham’s office in 2020, two other prosecutors on Durham’s team reportedly left later after raising concerns about the wisdom of pursuing a prosecution against a lawyer with ties to Clinton’s campaign that ultimately led to an acquittal.

For ex-DoJ leaders and top Democrats, the latest allegations about the political motives that drove Durham and Barr underscore earlier signs that the ‘investigation into the investigators” was handled improperly.

“The Durham special counsel investigation was tainted from the outset by the excessive involvement of attorney general Barr and its reaching significant conclusions before it had done any significant investigation,” said the ex-DoJ inspector general Michael Bromwich.

Bromwich added: “From the outset, there was no pretense that this was an independent investigation in which the facts would determine the outcome. The scorecard: an interminable, four-year investigation; a single conviction based on a case handed over by the IG on a silver platter; and two humiliating acquittals. There has never been a record like that in the half-century history of independent counsels and special counsels.”

Top Democrats too are incensed by the conduct of the Durham investigation and Barr’s role in the inquiry.

Congressman Jamie Raskin, the top Democrat on the House oversight committee who served on the House January 6 select committee that investigated the Capitol insurrection, said:

“The whole course of the Durham investigation suggests the heights of prosecutorial misconduct. It’s hard to imagine a better case study of the weaponization of Justice than what Barr was doing with the Durham inquiry.”

The Senate judiciary committee chairman, Richard Durbin, said: “These reports about abuses in special counsel Durham’s investigation – so outrageous that even his longtime colleagues quit in protest – are but one of many instances where former President Trump and his allies weaponized the justice department. The justice department should work on behalf of the American people, not for the personal benefit of any president.”

Durbin added that the Senate judiciary committee would “take a hard look at these repeated episodes, and the regulations and policies that enabled them, to ensure such abuses of power cannot happen again”.

Last September, Durbin notified DoJ that the judiciary panel planned to look into explosive details in a book by Geoffrey Berman, the ex-chief of DoJ’s southern district office in Manhattan, about political interference by Barr and Trump loyalists in several investigations.

Berman wrote that Barr in 2019 sought unsuccessfully to pressure him to reverse the conviction of Trump’s ex-lawyer Michael Cohen on campaign finance violations, and to block related investigations into potential campaign finance violations.

Barr also pressured Berman to resign with an eye to replacing him with a Trump loyalist, but after Berman refused to step down Trump fired him.

Together, the charges by Berman, and the evidence amassed by the Times, paint a troubling picture of how Barr seemed to lean over backwards to boost Trump politically, until after the 2020 election when Barr eventually publicly rejected Trump’s claims of fraud.

The justice department did not respond to requests from the Guardian seeking a comment from Durham who is expected to write a final report about his inquiry later this year. Dannehy also did not reply to phone messages asking for comment.

Barr last week told the Los Angeles Times: “The idea that there was a thin basis for doing [the Durham investigation] doesn’t hold water.” Barr added that “one of the duties of the attorney general is to protect against the abuse of criminal and intelligence powers, that they’re not abused to impinge on political activity, so I felt it was my duty to find out what happened there”.

Critics note that Barr’s defense is weak since Durham was tapped just a month after special counsel Robert Mueller issued an extensive report documenting substantial ties between Trump’s campaign and Russia, and concluded that Moscow tried to sway the election to help Trump in “sweeping” and “systematic” ways.

Barr’s defense of the Durham investigation’s launch looks shaky too, given public comments Barr made in congressional testimony at a Senate committee hearing in 2019. Barr was asked several times by then senator Kamala Harris if Trump or any White House officials had suggested or pressured him to launch his sweeping review. Barr was evasive, but acknowledged some “discussions” of the matter had occurred, adding “they have not asked me to open an investigation”.

For Raskin, the growing evidence of misconduct in the Durham investigation comes at an ironic moment, as the House Republican majority has created a special panel on the judiciary committee to look into the “weaponization of the government” that’s expected to focus heavily on the Biden administration and the Department of Justice and the FBI.

The Republican majority “created a weaponization committee which is a precise and accurate description of their own activities in transforming the government to be a political weapon for Donald Trump and his inner circle”, Raskin said. “Of course, they don’t have any interest in looking at the corruption of the justice system under Trump.”