“In his motion, the Special Counsel contrives dubious allegations of witness tampering,” wrote Manafort lawyer Kevin Downing in his client's response to the special counsel's most recent measure against Manafort.
“From a scant record, the special counsel conjures a sinister plot to ‘corruptly persuade’ two of Mr. Manafort’s former business associates to perjure themselves at the upcoming trial in September.”
In a court filing Monday night, attorneys with the special counsel accused Manafort of "attempting to tamper with potential witnesses" while awaiting his trial, which thereby "has violated the conditions of his release."
On Friday, the special counsel hit Manafort with a third superseding indictment and charged Manafort's business associate -- a Russian national with ties to Russian intelligence, Konstantin Kilimnik -- with conspiracy to obstruct justice and obstruction of justice.
According to the special counsel, in February, within days of Mueller's filing a 32-count superseding indictment against Manafort, the former Trump campaign chairman allegedly contacted two individuals who worked with him on a lobbying scheme to aid his Kremlin-backed Ukrainian clients.
The two individuals were members of the "Hapsburg group," described by Mueller in the February superseding indictment of Manafort as "a group of former senior European politicians to take positions favorable to Ukraine, including by lobbying in the United States."
"Exhibits attached to the special counsel’s filing support the defendant’s position that the mission and work of the so-called Hapsburg Group was European-focused and that the text messages cited by the Special Counsel do not establish any witness tampering,” Manafort’s lawyer said in a filing Friday night.
“While the special counsel’s motion generated enormous negative media coverage against Mr. Manafort, the special counsel’s actual ‘proof’ in the motion is virtually nonexistent.”
Manafort faces lengthy indictments in both Washington, D.C., and Virginia on charges of bank fraud, tax evasion, money laundering, false statements, conspiracy, and failure to register as a foreign agent for past work on behalf of Ukraine.
Mueller's team is asking the Washington, D.C., federal court to revoke Manafort's current $10 million bail and is asking that the court "promptly schedule the hearing called for by the statute to determine Manafort's release status.”
The government has not charged Manafort with the crime of witness-tampering or obstruction of justice. A hearing on the matter has been set for June 15.
"Mr. Manafort is innocent and nothing about this latest allegation changes our defense," Manafort spokesperson Jason Maloni told ABC News in a statement on Tuesday. "We will do our talking in court," Maloni added.
Representatives for the special counsel's office declined to comment to ABC News.
ABC News' Benjamin Siegel contributed to this report.