Paul Manafort, center, President Donald Trump's former campaign chairman, walks with this wife Kathleen Manafort, right, and Jason Maloni, Manafort's spokesman, left, as they arrived at the Alexandria Federal Courthouse for an arraignment on his Eastern District of Virginia charges March 8. (Jacquelyn Martin/AP)

Former Trump campaign chairman Paul J. Manafort asked a federal court Tuesday to toss out 18 criminal charges against him in Virginia, sharpening his challenge to the legitimacy of special counsel Robert S. Mueller III’s investigation into alleged Russian interference in the 2016 U.S. election.

The pretrial motions to dismiss an indictment intensified a legal attack mounted by Manafort in a lawsuit in January. In that lawsuit, Manafort contends Mueller has exceeded his legal authority and is asking to void the Justice Department’s appointment of him.

Manafort’s attorneys in January and again in a longer, 38-page filing Tuesday argued that acting attorney general Rod J. Rosenstein improperly ordered Mueller to investigate “links and/or coordination” between the Russian government and Trump campaign, as well as “any matters that arose or may arise directly from” that investigation.

The order gave Mueller “a blank check” that “the Special Counsel has cashed, repeatedly” to prosecute Manafort for alleged conduct that did not arise from the investigation and predates the campaign and which, Manafort’s attorneys argue, prosecutors knew about and declined to pursue in 2014.

The filings were made by Manafort attorneys Kevin M. Downing and Thomas E. Zehnle.

The Justice Department has defended Mueller’s appointment, and said the proper forum for Manafort to challenge his charges is his criminal case

Manafort, 68, and his longtime deputy, Rick Gates, 45, pleaded not guilty in October to a 12-count indictment in federal court in the District of Columbia accusing them of conspiring to defraud the United States by laundering $30 million since 2006 from their work for a Russia-friendly political party in Ukraine and former Ukrainian president Viktor Yanukovych.

Gates pleaded guilty to reduced charges in a cooperation deal last month, while Mueller’s team added tax evasion and bank fraud charges against Manafort in Alexandria federal court. Prosecutors also transferred other charges — that Manafort failed to follow lobbying disclosure laws and worked as an unregistered foreign agent — from the District case.

Tuesday’s filing presses an argument similar to the one Manafort’s defense raised March 16 when they asked to have five remaining D.C. charges dismissed. Manafort’s lawyers contend the special counsel’s “sprawling” investigation and “unbounded exercise of prosecutorial authority is wholly incompatible with our constitutional tradition.”

Manafort has pleaded not guilty to all charges, and said his Ukraine work ended in 2014.

He joined the Trump campaign in March 2016 and chaired it from June to August.

“None of the alleged conduct has any connection to coordination between the Trump presidential campaign [in 2016] and the Russian government,” Manafort’s lawyers wrote. The Justice Department was already aware of Manafort’s work because he disclosed it to them in 2014 and had decided not to prosecute, his lawyers argued, and so discoveries of his conduct did not “arise” in the Mueller probe.

They added, Manafort “faces a game of criminal-procedure whack-a-mole against a Special Counsel whose massive resources he cannot possibly hope to match.”

A Justice department motion to toss out Manafort’s lawsuit is set t be heard in Washington April 4.

Prosecutors are set to respond next week in federal court in the District to his criminal case filings ahead of a scheduled September trial date in Washington. A July 10 trial date is scheduled in federal court in Alexandria.

Earlier this month, joined by attorney Richard Westling, Manafort’s defense also asked to have a forfeiture claim against Manafort — a potential $30 million penalty if convicted — and a money laundering charge dismissed, arguing the incidents in the accusations did not result from illegal activity because Manafort’s alleged crime was not his foreign lobbying work, but his failure to register as a foreign agent.

Manafort also asked to drop one of two charges in the District that his lawyers argued stemmed from the same alleged false statement submitted in Foreign Agent Registration Act filings.