A conservative retired federal judge on Wednesday condemned former President Donald Trump's criticisms of judges hearing criminal cases brought against him, calling the recent attacks "unprecedented" and "inexcusable."

"The former president's comments and attacks on the federal judiciary and on the specific individual judges who will preside over his trials are unprecedented in American history," J. Michael Luttig told CNN's Anderson Cooper on "AC360."

"They are a grave disservice to the nation. They are inexcusable. And they imperil the former president himself, in the defense of his actions on January 6, before the juries that will hear his case," he continued. "But this is, of course, a pattern that the former president has engaged in since" assuming office.

Trump -- who is facing 91 charges across four separate indictments at the same time that he's seeking the Republican presidential nomination in 2024 -- has insisted it is his First Amendment right to defend himself publicly and views social media as his most direct way of communicating with voters, as CNN previously reported.

Over the weekend, the former president railed against the judge overseeing his criminal case in Washington, DC, over his attempts to overturn the 2020 election after she warned him not to intimidate witnesses, obstruct justice or try to muddy his ability to have a fair trial.

Trump criticized Judge Tanya Chutkan, an Obama appointee, on Truth Social as "highly partisan" and "very biased & unfair."

Asked whether the courts will be able to work out a trial schedule for Trump, Luttig -- a former judge on the 4th US Circuit Court of Appeals -- told Cooper he "believe(s) that the courts involved will cooperate with each other and sequence the trials in such a manner as to ensure that the former president is tried on all of these matters before the 2024 election."

Luttig was an adviser to former Vice President Mike Pence, who relied on his guidance when he decided to defy Trump and certify the Electoral College vote, as well as a key witness before the House select committee that investigated the January 6, 2021, attack on the US Capitol.

He has emerged as a vocal critic of both Trump and the Republican Party, warning last week on CNN that the former president is even more dangerous than he was in the aftermath of the 2020 election and that "American democracy is in grave peril."