Rick Gates, a former campaign official for U.S. President Donald Trump, departs U.S. District Court after he and Trump's former campaign manager Paul Manafort attended a hearing in the first charges stemming from a special counsel investigation of possible Russian meddling in the 2016 presidential election in Washington, U.S., October 30, 2017.

Paul Manafort's defense attorneys on Wednesday raised the possibility that Rick Gates had engaged in as many as four extramarital affairs, as they sought to discredit the prosecution's star witness by suggesting the married father of four had lived a "secret life" years ago.

"Do you recall telling the special counsel that you had four extramarital affairs?" Kevin Downing, Manafort's attorney, asked, according to NBC News.

After prosecutors objected to the question, Downing insisted that it was relevant because it could show that Gates had lied in his previous testimony, he said.

Manafort's attorneys did not present evidence of the multiple affairs, and Gates did not get a chance to answer the question directly as the defense moved on to other topics.

On further questioning, Gates said, "I've made many mistakes over many years."

Gates testified on Tuesday however that he had an extramarital relationship years earlier. The admission came after Downing accused him of living a "secret life" in which Gates used funds embezzled from Manafort to support his philandering in a secret London apartment. During his cross-examination, Gates denied using funds embezzled from Manafort to support the affair.

Gates is the central figure in the case for Manafort's lawyers, who are looking to undercut his credibility as a truthful witness as he testifies that Manafort directed him to commit financial crimes.

Manafort's former protege pleaded guilty in February to lying to special counsel Robert Mueller's investigators and cut a plea deal that drastically reduced his potential sentence in exchange for his full cooperation with their probe of potential Russian coordination with the Trump campaign.

Manafort has pleaded not guilty to all charges in the case, which is being tried in U.S. District Court in Virginia. The charges include multiple counts of bank fraud and filing false income tax returns. If convicted, Manafort could be sentenced to as much as 30 years in prison for each of the most serious counts.

Gates also told prosecutors on Tuesday that Manafort had suggested appointing banker Stephen Calk to a role in the Trump administration after the 2016 presidential election. Calk's bank had reportedly loaned Manafort $16 million in home loans from December 2016 to early 2017.

"We need to discuss Steve Calk for Sec of the Army," Manafort wrote Gates in a November 2016 email presented by prosecutors.