The head of a Senate panel investigating Clarence Thomas said Monday that the Supreme Court justice had failed to disclose additional private jet travel.

In a letter to an attorney for conservative megadonor Harlan Crow, Sen. Ron Wyden, D-Ore., said flight records show that in 2010 Thomas and his wife traveled round-trip from Hawaii to New Zealand aboard Crow’s private jet.

Wyden, who chairs the Senate Finance Committee, said the finding intensified his concerns that Crow was engaged in a scheme to avoid paying taxes.

“I am deeply concerned that Mr. Crow may have been showering a public official with extravagant gifts, then writing off those gifts to lower his tax bill,” Wyden wrote.

The letter, which also cited reports of Thomas’ travel to Greece, the Caribbean, Russia and the Baltics, is the latest in a string of allegations from Senate Democrats about undisclosed travel by Thomas. The Senate Judiciary Committee released records in June showing other undisclosed trips.

In a statement Monday, Crow’s office accused Wyden of “abusing” his panel’s power in what it called a political campaign against the Supreme Court. Crow’s office added that his attorneys “have already addressed Senator Wyden’s inquiries, which have no legal basis and are only intended to harass a private citizen.”

“Mr. Crow and his businesses are in good standing with the IRS. He has always followed applicable tax law as advised by national accounting firms who serve as his tax advisors,” his office said.

An attorney for Thomas and a spokesperson for the Supreme Court did not immediately respond to requests for comment Monday.

Thomas acknowledged a pair of trips in 2019 with Crow in his annual financial disclosure report in June.

The judiciary has updated its disclosure rules to make it clear that private jet travel has to be reported.

Thomas’ attorney, Elliot S. Berke, said in June that a provision by the Judicial Conference allowed for a personal hospitality exemption and that Thomas “has fully complied with the new disclosure requirement.”

The Supreme Court has come under increasing internal and external pressure to develop an enforceable code of ethics for the justices. President Joe Biden recently backed changes involving term limits and ethics for justices, while conservative Justice Neil Gorsuch warned that Biden needs to “be careful” with the changes he’s backing.