A handful of Volkswagen consumers who opted out of the "clean diesel" class action settlements have filed a motion to disqualify U.S. District Judge Charles Breyer from next week's trial.

In a Wednesday motion, lawyers for 10 plaintiffs suing Volkswagen for fraud damages said that the Northern District of California judge had raised "concerns about appearance of bias" after he ruled this month to make the trial's first phase a bench trial focused on the fairness of the "clean diesel" settlements, the same ones that he approved.

That first phase starts Monday.

"Judge Breyer has a dog in this fight," wrote Bryan Altman, of Altman Law Group in Los Angeles, and Lauren Ungs, managing partner of Knight Law Group's office in Oakland, California, in the disqualification motion. "He has a vested interest in determining that the settlement he presided over and approved was a fair resolution of consumer claims."

In an interview, Altman said the plaintiffs' team had hoped not to bring the disqualification motion, but Breyer's rulings and comments in court necessitated its filing.

"It's regrettable where we come to the point where we felt compelled to do this, so our clients get their day in court and a fair trial," he said.

On Thursday, Volkswagen's lawyers opposed the motion, calling it "baseless and unwarranted" and a "frivolous tactic to try to delay the trial."

"The fact that this court has presided over the resolution of the class action settlement is no basis for recusal," wrote Volkswagen's lawyer, Robert Giuffra, a partner at Sullivan & Cromwell in New York. "Courts routinely preside over the resolution of class actions and the subsequent trial of opt-out litigation, such as this."

The motion, he wrote, was another example of the "modus operandi" of both plaintiffs' firms, which have sought disqualification of judges in several of their cases.

Giuffra declined to comment, and a Volkswagen representative did not respond to a request for comment.

The disqualification motion is the latest twist in a case that followed Volkswagen's $14.7 billion class action settlement in 2016 and $1.2 billion agreement in 2017 to resolve consumer claims associated with its "clean diesel" scandal, in which the automaker admitted to cheating on emissions tests. Under the settlements, Volkswagen agreed to provide cash and repairs to customers.

The plaintiffs, the majority of whom are "low income," according to their lawyers, are seeking damages under the California Consumer Legal Remedies Act. The act provides for compensatory and punitive damages, as well as attorney fees.

Last month, plaintiffs sought to bring former FBI Director Louis Freeh into the case, prompting Volkswagen to file a motion to disqualify him as an expert. The motion noted that, in 2016, Volkswagen had considered hiring Freeh as a consultant on the diesel scandal, for $15 million a year, but decided against it. In next week's trial, Freeh was set to testify that the government settlement in the related criminal case should have been much higher.

Breyer excluded Freeh as an expert on Feb. 11, mooting Volkswagen's disqualification motion.

The disqualification motion dates back to a Feb. 4 summary judgment ruling in which Breyer found that Volkswagen's affirmative defense to plaintiffs' consumer fraud claims should go before him, rather than a jury. In particular, Volkswagen planned to argue that its "clean diesel" settlements provided an "appropriate correction" to any consumer fraud claims.

That issue is now part of a bench trial starting Monday, with a jury expected to arrive on Tuesday for the next phase focused on compensatory damages. A third phase about punitive damages, if necessary, would follow immediately.

Plaintiffs insisted, in their disqualification motion, that Breyer now had a conflict.

"It appears at least that the court will be looking at the class action settlement and making a determination that that was an adequate response, and the judge was the one principally involved in the class action settlement," Altman said.

There are other concerns, Altman said, such as comments that Breyer made in court and rulings against the plaintiffs, such as one prohibiting them from arguing the vehicles had no value.

Not liking Breyer's rulings is not a reason to disqualify him, Volkswagen's lawyers wrote in Thursday's filing. They added that plaintiffs lawyers, at a Feb. 13 hearing, supported putting the consumer fraud defense before a judge instead of a jury.

They also cited four other cases in which the same plaintiffs firms had brought disqualification motions. The plaintiffs also tried to disqualify the magistrate judge overseeing settlement discussions in the Volkswagen case, they wrote.

Altman acknowledged that he supported a bench trial on the consumer fraud defense, but said another judge should oversee it, not Breyer. As to the other cases in which his firm or Knight Law Group brought disqualification motions, he said they were irrelevant to the Volkswagen case.

"Over the course of time, it's always incumbent on an attorney who zealously represents the interests of a client to do what is appropriate and take what steps are appropriate to ensure a fair trial," he said. "There have been instances over the course of time where bench officers have conducted themselves in ways that are hostile or prejudicial to one party or the other. It's incumbent on any attorney to try to address that."