As questions swirl about his credibility, former Trump campaign adviser Roger Stone settled a defamation suit seeking $100 million in damages on Monday for publishing false and misleading statements on InfoWars.com, a far-right website known for promoting conspiracy theories.

The agreement requires Mr. Stone to run ads in national newspapers, including The Wall Street Journal, apologizing for making defamatory statements about a Chinese businessman who is a vocal critic of Beijing. It also requires Mr. Stone to publish a retraction of the false statements on social media. Doing so exempts him from paying any of the damages.

In a text message, Mr. Stone described his conduct as “irresponsible” and added that “I am solely responsible for fulfilling the terms of the settlement.”

Unrelated to the Russia probe, Mr. Stone’s settlement is the latest indication that his use of various media platforms to spread unfounded claims isn’t without consequences. Special counsel Robert Mueller’s office is investigating Mr. Stone’s role in orchestrating stories about key events being examined in the Russia probe, the Journal has reported.

Rep. Adam Schiff (D., Calif.), who is expected to take control of the House Intelligence Committee, said on Sunday of Mr. Stone’s testimony last year: “I believe there’s ample reason to be concerned about his truthfulness.” Mr. Stone has accused Mr. Schiff of “smear tactics” and said he stands by his testimony.