In December, Mueller's team wrote in a heavily-redacted court filing that Manafort "breached his plea agreement in numerous ways by lying to the Federal Bureau of Investigation and Special Counsel's Office".
Mueller said in a court filing last month that Manafort broke his plea deal by lying about his contacts with Russian officials and the White House while he was in prison.
In the document Manafort's lawyers referenced a December court filing in which Mueller alleged that Manafort had "conceded" to discussing the peace plan, which they argued was an indication that their client was forthcoming when his memory was refreshed of past events.
Manafort's lawyers say he was awakened before dawn on the days he was interviewed and normally spent the entire day talking with investigators. Reuters did not independently review the filing, which was soon replaced in the public database with a properly redacted version.
But unfortunately for Manafort, his lawyers inadvertently ended up revealing new details about Manafort's alleged misdeeds by improperly redacting their court filing, as first reported by Guardian reporter Jon Swaine.
In fact, during a proffer meeting held with the Special Counsel on September 11, 2018, Mr. Manafort explained to the Government attorneys and investigators that he would have given the Ukrainian peace plan more thought, had the issue not been raised during the period he was engaged with work related to the presidential campaign.
Mueller's team also indicted Kilimnik for witness tampering in Manafort's case. While it is unknown if the 2016 polling data was related to the Trump campaign, the fact that Manafort was the chairman of the Trump campaign during 2016, certainly doesn't bode well for those still denying that there was no collusion between the campaign and Russian Federation.
The latest allegations further detail how Manafort's work on the campaign intersected with his past worldwide work with Kilimnik.
Mueller's filing said Manafort "breached his plea agreement in numerous ways by lying to the Federal Bureau of Investigation", including about his interactions with Russian associate Konstantin Kilimnik.
The filing did not provide further details on the Madrid meeting or the peace plan, although Mueller has scrutinized a proposal by a Ukrainian lawmaker that involved, among other outcomes, the lifting of USA sanctions on Russian Federation, according to people familiar with the matter.
In addition, the defense document discloses a meeting in Madrid between Manafort and Kilimnik. Manafort spokesman Jason Maloni said Tuesday the Madrid trip mentioned in the filing occurred in January or February 2017- months after Manafort was ousted from the campaign and as Trump was taking office.
Manafort dangled the briefings as he was mired in a dispute with Mr Deripaska over a multi-million-dollar deal involving a Ukrainian cable company.
Manafort faces a tentative March 5 sentencing date in his federal case in D.C. If he is found to have breached the deal, he would lose any sentencing credits for acceptance of responsibility, prosecutors said.
The defence team says Mr Mueller's team has indicated it will not pursue additional charges against Manafort.
In the filing Manafort's lawyers said they would not seek an evidentiary hearing to contest Mueller's allegations of lying, arguing that such factual matters could be addressed in a pre-sentencing report.