Hunter Biden filed a motion in federal court Wednesday to subpoena former President Donald Trump, former Attorney General William Barr and other former Justice Department officials for documents and materials that his legal counsel alleges were part of a partisan pressure campaign to pursue investigations into the president's son. 

In the court filing, Hunter Biden argues communications between Trump and former Justice Department officials during his presidency reveal "more than a mere appearance that President Trump improperly and unrelentingly pressured DOJ to pursue an investigation and prosecution of Mr. Biden to advance President Trump's partisan ambitions." 

The motion filed in Delaware is part of Hunter Biden's defense in a federal trial to which he pleaded not guilty to three felony counts related to his purchase and possession of a firearm in 2018 when he was a drug user. A plea agreement between the government and Biden's team that encompassed both the unlawful purchase of a firearm and misdemeanor tax charges collapsed in July after a federal judge questioned the terms. 

Hunter Biden argued in the filing that a push for more severe charges against him in the wake of the collapsed plea deal was part of partisan effort to make his prosecution an "election issue." 

The motion includes subpoena requests for materials Biden's defense claims are pertinent to evidentiary hearings, from former Justice Department officials Jeffrey Rosen and Richard Donoghue, who testified before the bipartisan Jan. 6 House select committee that Trump warned that "people will criticize the DOJ if [Hunter Biden] is not investigated for real," according to Donoghue's notes from the call, as read in his testimony.  

The ongoing investigation into Hunter Biden, now led by special counsel David Weiss, spanned five years over the course of both the Trump administration and that of his father, President Joe Biden. Republican-led congressional committees probing Hunter Biden's personal finances and his foreign business dealings, have centered much of their investigative focus on whether senior officials in the Biden administration took steps to impede criminal probes into the president's son, and whether President Biden himself benefitted from any foreign business brokered by members of his family. 

IRS whistleblowers Gary Shapley and Joseph Ziegler, case agents previously assigned to the Hunter Biden investigation told lawmakers they recommended federal charges be brought against the president's son for tax evasion and other violations but faced resistance and were told that then-U.S. Attorney David Weiss was denied special counsel status at the time and "not the deciding person" to bring charges in the case. They alleged intentional slow-walking and "an undeniable pattern of preferential treatment" in the federal investigation into Biden.   

In a closed-door testimony before the House Judiciary Committee in November, Weiss disputed those claims, asserting he had full authority to pursue charges against Hunter Biden. "At no time was I blocked, or otherwise prevented from pursuing charges or taking the steps necessary in the investigation by other United States Attorneys, the Tax Division or anyone else at the Department of Justice," he said.  

Hunter Biden's lawyer argues in this latest court filing that the requested documents, records, memoranda and other materials from Trump, and former Justice Department officials Barr, Donoghue and Rosen go to the "heart of his defense that this is, possibly, a vindictive or selective prosecution arising from an unrelenting pressure campaign beginning in the last administration, in violation of Mr. Biden's Fifth Amendment rights under the Constitution." 

Barr and an attorney for Rosen declined to comment.

CBS News has reached out to a Trump spokesperson.

Catherine Herridge contributed to this report.

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