Steven Donziger, talking to press outside the courthouse in 2015. NYLJ/Mark Hamblett

This story has been updated with Seward & Kissel's response Friday.

Steven Donziger, the suspended lawyer who is facing criminal contempt charges stemming from his long fight with Chevron over environmental contamination in Ecuador, has asked a federal judge to force court-appointed prosecutors at Seward & Kissel to disclose any ties their firm has to the oil giant.

Seward & Kissel lawyers Rita Glavin, Brian Maloney and Sareen Armani were appointed last August to prosecute Donziger for criminal contempt for allegedly flouting a discovery order in a lawsuit brought by Chevron. The U.S. Attorney's Office in the Southern District of New York declined to take up the criminal contempt case, leading to the unusual appointment of private prosecutors for a public prosecution.

In a Tuesday letter to U.S. District Judge Loretta Preska of the Southern District of New York, Donziger's lawyer, Andrew Frisch, said his research led him to believe that an unnamed Seward & Kissel partner served on Chevron's board and that the firm served clients who do business with Chevron or related entities. He said Glavin "has declined to answer my questions about Seward's ties to Chevron."

It wasn't clear Friday which people or entities Frisch was referring to. But one area of overlap between Chevron and Seward & Kissel is the shipping industry. Few law firms have maritime law practices that are as robust as Seward & Kissel's, and Chevron's oil and liquified natural gas are transported globally on ships.

Another possible overlap is Oaktree Capital Management. Frisch's letter referred to a Chevron board member who is the vice-chairman of an investment fund that has funded at least two of Seward & Kissel's clients. Chevron director John Frank is Oaktree's vice chairman, and Oaktree is listed as an investor on at least two deals listed on Seward & Kissel's website.

In a response filed later Friday, Glavin said it was simply not true that any Seward partner had been on Chevron's board. As to the allegation that its clients had done business with Chevron, she wrote, "even if true, this creates no conflict or conflicting loyalty for the prosecution team in this criminal case."

"Prior to taking on this representation, Seward performed appropriate conflict checks (as it does before taking on any representation)," she wrote. She said the case law cited by Donziger didn't apply.

Frisch's letter Tuesday also called for Glavin and her colleagues to disclose any communications they have had with the chambers of U.S. District Judge Lewis Kaplan of the Southern District of New York, who appointed them to prosecute Donziger. Frisch said it was "it is important to clarify whether and the extent to which" the judge has played a role in the prosecution.

In response to Donziger's question about contacts with Judge Kaplan, Glavin wrote, "the prosecution does not work for Judge Kaplan and makes its own decisions in this case."

Glavin and Frisch declined to comment.

The letters come as Donziger facing legal threats on three fronts. The suspended attorney, who has been subject to home confinement for several months, won a $9 billion judgment against Chevron in Ecuador's courts in 2011, but Chevron successfully argued in U.S. courts that the judgment was obtained through bribery. The oil giant, in turn, won an $800,000 judgment against Donziger and has tried to enforce it and to have him disbarred.

While the criminal contempt case advances, Donziger has sought to partly pause the civil case brought by Chevron, which is seeking to enforce its judgment. He appealed a Dec. 9 decision by Kaplan rejecting his motion in that case. He has also asked the U.S. Court of Appeals for the Second Circuit to reverse a decision by Preska to keep him subject to home confinement.

In the meantime, potential disbarment proceedings have been ongoing in New York state courts. Referee John Horan heard several days of testimony in October and posttrial briefs were filed in December.