Senate Finance Committee Chair Ron Wyden revealed on Monday that Supreme Court Justice Clarence Thomas had failed to disclose even more flights aboard a private jet owned by Republican mega-donor Harlan Crow than were previously known.

In a letter to an attorney representing Crow, the Oregon Democrat also demanded travel and financial records related to Crow’s superyacht, the Michaela Rose, and the relationship between the justice and his billionaire benefactor. Crow’s legal team has repeatedly avoided providing such records, but Wyden said they could help determine whether the real estate mogul claimed business deductions on personal trips aboard luxury craft ― including those with Thomas ― to evade taxes.

“On several occasions, I have asked directly how many times Justice Thomas traveled aboard the Michaela Rose and private jets paid for by Mr. Crow, and whether Mr. Crow deducted the costs of these particular trips on tax filings. These should not be difficult questions to answer,” Wyden wrote to the attorney. “The possibility that Mr. Crow may have lavished secret gifts on a sitting Supreme Court justice and then impermissibly reduced his taxable income by millions of dollars with impunity requires legislative scrutiny.”

A spokesperson for the Supreme Court did not immediately respond to HuffPost’s request for comment. A spokesperson for Crow told The New York Times that Wyden’s inquiries have “no legal basis” and that the real estate mogul has “always followed applicable tax law.”

Wyden’s committee has opened an inquiry into Crow and Thomas’ financial relationship as top Democrats work to bring major ethics reform to the Supreme Court. Reports that multiple justices failed to disclose luxury gifts and travel from ultrarich benefactors have led Democrats, including President Joe Biden, to call for term limits and a code of conduct that is enforceable.

A ProPublica investigation last year showed that Thomas accepted at least two luxury trips in 2019 from Crow that were not included in financial disclosure forms. The veteran conservative justice claimed he did not know he had to disclose gifts of personal “hospitality” from friends who did not have cases before the high court, but he amended his forms to confirm those two trips in his annual financial disclosure in June.

But just a week after that annual disclosure’s release, the Senate Judiciary Committee found that Thomas failed to disclose at least three additional trips on Crow’s private jet from 2017 to 2021. That information was provided to the committee by Crow himself in response to a subpoena.

And in Monday’s letter, Wyden said his committee found yet another undisclosed trip funded by the political mega-donor. According to international flight records from U.S. Customs and Border Protection, Thomas took a round trip from Hawaii to New Zealand aboard Crow’s private jet with his wife, Ginni Thomas, who is a conservative activist, and Crow himself. The three first flew on Nov. 19, 2010, and returned on Nov. 27.

Despite Thomas having amended past records to disclose the luxury travel that Crow provided, the justice never revised his 2010 form to include the international private jet trips he took that year.

In addition to the New Zealand flights, Wyden’s letter included reports that Thomas joined Crow on trips to Greece, Russia and the Baltics via private jet. None of those trips is in Thomas’ financial disclosure forms.

“The fact a Supreme Court justice accepted free travel to Russia paid for by a billionaire and failed to disclose the trip as required by law is undoubtedly concerning and merits continued investigation,” Wyden wrote. “Other government officials have been charged for making false statements on financial disclosures for less serious violations than the evidence suggests Justice Thomas committed.”

Thomas has accepted at least $4 million in gifts since becoming a Supreme Court justice three decades ago, according to Fix the Court, a judicial reform nonprofit. That number is nearly 10 times the combined value of all gifts received by his colleagues during the same period.

“Supreme Court justices should not be accepting gifts, let alone the hundreds of freebies worth millions of dollars they’ve received over the years,” Gabe Roth, the executive director of Fix the Court, said in a June 6 statement.

“The ethics crisis at the Court won’t begin to abate until justices adopt stricter gift acceptance rules,” Roth said.