Jeffrey Clark, a former top environmental lawyer at the Trump justice department accused of plotting with Trump to undermine the 2020 election results in Georgia and other states, is facing ethics investigations in Washington that could lead to possible disbarment, as well as a watchdog inquiry that might result in a criminal referral.

The mounting scrutiny of the ex-assistant attorney general, who led the justice department’s environment division for almost two years and then ran its civil division, was provoked by a report from the Senate judiciary committee whose Democratic chairman, Richard Durbin, has asked the DC bar’s disciplinary counsel to examine Clark’s conduct and possibly sanction him.

The panel’s exhaustive 394-page report followed an eight-month inquiry, and included voluntary testimony from former acting attorney general Jeffrey Rosen and his deputy, Richard Donoghue, revealing how Clark schemed privately with Trump about ways to pressure Rosen to help launch an inquiry into baseless charges of voting fraud in Georgia and other states that Joe Biden won.

The report noted Clark repeatedly tried to “induce Rosen into helping Trump’s election subversion scheme”, including by telling Rosen that if he agreed to join their cabal to overturn election results, Clark would turn down an offer Trump had made him to become attorney general in place of Rosen.

Clark was asked by the Senate panel to testify voluntarily in July but declined, according to a source familiar with the matter.

The Senate report was shared with the House select committee that has been investigating the 6 January attack on the Capitol by Trump supporters, and Trump’s efforts to overturn the election results. On 13 October, the committee issued a subpoena seeking deposition testimony, and it requested records from Clark on 29 October, after reportedly struggling to get his cooperation.

“It’s no mystery why Clark is playing hard to get with Congress,” said former justice department inspector general Michael Bromwich in an interview with the Guardian. “He faces a meaningful threat of criminal liability based on the facts contained in the Senate report.

“The Senate report provides overwhelming evidence that Jeffrey Clark became a witting pawn of Trump’s in trying to launch a coup in the justice department, which would then serve as the launching pad for the broader coup whose aim was to overturn the results of the election.”

Clark’s covert efforts to help Trump have been under scrutiny by the current inspector general at the justice department, Michael Horowitz, since January, when news reports surfaced about his machinations with Trump to help overturn the election results by spurring an investigation in Georgia focused on baseless claims of voting fraud.

It’s unclear when the inspector general inquiry will be concluded, but depending on the findings, a criminal referral could result.

The Senate report provided new details about the secretive pressure tactics deployed by Trump and Clark to persuade Rosen to accede to their schemes to help nullify Biden’s win, even after Trump staunch ally, attorney general William Barr, publicly stated on 1 December that the election results were not marred by fraud that “could have effected a different outcome in the election”.

Strikingly, the report described a bizarre multi-hour White House meeting on 3 January that was attended by Trump, Rosen, Clark and other top administration lawyers, where Trump initially showed strong interest in ousting Rosen, who had been resisting pressures from Clark to open an inquiry into fraud allegations, and replacing him with Clark.

According to Rosen’s testimony, Trump began the meeting by taking an aggressive posture and declaring: “One thing we know is you, Rosen, aren’t going to do anything to overturn the election.”

At the end of the meeting, Trump dropped the covert scheme to oust Rosen after Rosen’s deputy Donoghue told Trump that he, Rosen and others, including the two top White House attorneys, would resign in protest.

Pat Cipollone, the top White House lawyer, condemned Trump’s plan as a “murder-suicide pact,” according to the Senate report.

The Senate report formally recommended that the DC bar’s disciplinary counsel “evaluate Clark’s conduct to determine whether disciplinary action is warranted”.

Senator Sheldon Whitehouse, a top Democrat on the judiciary panel, in a statement to the Guardian said: “Either Jeffrey Clark was an enterprising sycophant looking to score points with a transactional president, or he was a cog in a much larger election-theft scheme.

“Clark’s testimony under oath will be very important to arrive at the full truth, which is why it’s very hard to imagine he avoids testifying – either before Congress or a grand jury.”

Before the release of the Senate report, ABC News unearthed emails revealing that Clark tried to get Rosen and his deputy to approve a letter he drafted on 28 December that would have pressed Georgia’s governor Brian Kemp to “convene a special session” of the state legislature to examine unfounded allegations of voting fraud before 6 January, when Congress met to certify the results.

The Senate GOP’s minority in a separate report offered a tepid defense for Trump and Clark’s actions, stating that Trump “listened to all data points” at the White House meeting where several resignations were threatened, and “rejected” the path Clark promoted with Trump’s apparent blessings. Grassley also faulted the Democrats for issuing their report before hearing from Clark and receiving more documents.

Still, two days before the majority report, about three dozen prominent lawyers and former DoJ officials signed an ethics complaint orchestrated by Lawyers Defending American Democracy which also asked the DC disciplinary counsel to investigate Clark’s conduct with an eye to sanctions.

The lawyers wrote that Clark “made false statements about the integrity of the election in a concerted effort to disseminate an official statement of the United States Department of Justice that the election results in multiple states were unreliable”.

Trump nominated Clark in mid-2017 to serve as assistant attorney general of the DoJ’s Environment and Natural Resources Division, but he was only narrowly confirmed in October 2018.

During his tenure running the division, Clark reportedly often was at odds with veteran lawyers there, because of his narrow reading of the Clean Air and Clean Water acts. By late 2020, Clark had become acting chief of the civil division at the DoJ.

Previously, Clark had been a partner at the powerhouse law firm Kirkland & Ellis, where he defended BP in Deepwater Horizon oil spill litigation and represented the US Chamber of Commerce in litigation that challenged the federal government’s power to regulate carbon emissions.

Barr and Rosen were also top partners at the firm before their stints leading the Department of Justice.

Clark’s distaste for strong environmental rules during his tenure at the department was presaged by some of his earlier comments about climate change in which he derided the need for more regulations to address it.

Clark, a member of the conservative Federalist Society, gave a talk at its 2010 convention, where he bitterly denounced the Obama administration’s policies to curb greenhouse gas emissions as “reminiscent of kind of a Leninistic program from the 1920s to seize control of the commanding heights of the economy.”

Given Clark’s anti-regulatory background in the private sector and his stint at the DoJ, it’s perhaps not surprising that he landed a top post working for the New Civil Liberties Alliance, a conservative law firm funded by the Charles G Koch Foundation.

Clark was tapped in July to be the alliance’s chief of litigation and director of strategy. Two calls to the alliance’s press office to reach Clark and seeking comment about his status there in the wake of the Senate report did not get responses. But on Wednesday Clark’s name had disappeared from its website’s roster of staff.