Former FBI Director James Comey speaks to the media after giving a private deposition to the House Judiciary and House Government and Oversight committees on Capitol Hill in Washington, U.S., December 7, 2018. REUTERS/Joshua Roberts

By Andrew Goudsward and Sarah N. Lynch

ALEXANDRIA, Virginia (Reuters) -Lawyers for former FBI Director James Comey renewed their bid to get federal criminal charges against him tossed out on Wednesday, arguing in court that President Donald Trump's personal animosity improperly motivated the prosecution.

A ruling in Comey's favor would be a major embarrassment for Trump's administration and would highlight a growing wave of skepticism within the judiciary about his efforts to prosecute political enemies.

"This is an extraordinary case and it merits an extraordinary remedy," Comey defense lawyer Michael Dreeben said at the start of arguments before U.S. District Judge Michael Nachmanoff in Alexandria, Virginia.

Dreeben called the case "a blatant use of criminal justice to achieve political ends."

Comey is among three prominent critics of the Republican president who have been hit with criminal charges by Trump's Justice Department in recent months. Trump critics have described the charges as a part of a campaign by the president to chill opposition. Comey pleaded not guilty after being charged in September with making false statements and obstructing a congressional investigation.

Wednesday's hearing is testing whether Trump's public calls for prosecuting perceived political enemies could derail the Justice Department's cases.

Nachmanoff is expected to weigh Trump's influence on prosecutors as he considers Comey's argument that the case is an improper "vindictive" prosecution brought solely to punish Comey for his criticism of Trump.

A VOW OF RETRIBUTION

Trump campaigned for the presidency last year in part on a vow of retribution and has demanded action against high-profile figures who have investigated or criticized him. Trump's Justice Department also has charged New York state Attorney General Letitia James, an elected Democrat, and John Bolton, Trump's former national security adviser.

The prosecution has accused Comey of lying to a Senate committee when he said he stood behind prior testimony denying that he authorized disclosures about FBI investigations to the news media.

Comey has launched a multi-pronged effort to have the charges dismissed before a trial.

His lawyers pointed to Trump's years of social media broadsides against Comey dating back to 2017, when Trump fired Comey as FBI director amid an investigation into contacts between Trump's 2016 presidential campaign and Russians. Comey later called Trump unfit for office.

They also cited Trump's decision to name Lindsey Halligan, the president's former personal lawyer who had no prior prosecutorial experience, as the interim U.S. attorney to take over the case after her predecessor was forced out in part over his reluctance to charge Comey.

Dreeben focused in particular on a September 20 social media post by Trump that was addressed to U.S. Attorney General Pam Bondi expressing frustration that "nothing is being done" to prosecute Comey and other political foes.

Trump's post was "effectively an admission that this is a political prosecution," Dreeben said.

Justice Department lawyer Tyler Lemons argued that Comey had not cleared the high legal bar to allow courts to second-guess charging decisions made by prosecutors.

HALLIGAN APPOINTMENT UNDER SCRUTINY

Halligan's role in cases against Comey and James has already come under intense scrutiny by courts.

A different judge - U.S. District Court Judge Cameron McGowan Currie - has expressed skepticism that Halligan was lawfully appointed as interim U.S. attorney for the Eastern District of Virginia, and is expected to rule on the issue before the Thanksgiving holiday on November 27.

Meanwhile, U.S. Magistrate Judge William Fitzpatrick, tasked with deciding certain pre-trial issues in Comey's case, indicated in a ruling this week that Halligan may have made significant legal errors before the grand jury that indicted Comey.

Motions relating to vindictive prosecution allow defendants to challenge criminal charges by arguing they were pursued as punishment for exercising legal rights. Those arguments are rarely successful, but they have received renewed attention as Trump wields the power of criminal prosecution against his critics.

James, whose office successfully sued Trump and his family business in a civil fraud case last year, has made a similar attempt to toss the mortgage-related charges brought against her.

(Reporting by Andrew Goudsward and Sarah N. Lynch; Additional reporting by Jan Wolfe;Editing by Scott Malone, Bill Berkrot and Will Dunham)