May 17 (UPI) — Senate Finance Chairman Ron Wyden on Wednesday again asked Republican donor Harlan Crow to disclose documents related to gifts that he gave Supreme Court Justice Clarence Thomas.

In a letter to Crow’s attorney, Wyden asked the billionaire to provide documents related to flight and yacht trips he took with Thomas, and property that he purchased from Thomas. Wyden said that he needs information on the real estate purchases to consider changes to gift tax laws.

“I believe that tax laws affecting enormous gifts and transfers of wealth by high-net individuals are in urgent need of reform,” Wyden said. “I also believe that, when appropriate, congressional oversight should be done in a manner that informs the public of the policy implications of the behavior being investigated.”

Democrats are concerned after revelations that Thomas accepted undisclosed, lavish gifts from a wealthy Republican donor, which were first reported by ProPublica last month.

Thomas and his wife reportedly accepted luxury trips from the Crow, a Dallas real estate mogul and Republican mega-donor, for years without disclosing the gifts. According to Wyden, chartering a yacht like Crow’s can cost as much as $245,000 or more.

Wyden initially sent a letter to Crow last month, requesting the documents.

“The secrecy surrounding your dealings with Justice Thomas is simply unacceptable,” Wyden wrote. “The American public deserves a full accounting of the full extent of your largesse towards Justice Thomas, including whether these gifts complied with all relevant federal tax and ethics laws.”

Crow has argued that Wyden’s requests are outside the scope of what his committee is allowed to investigate. He has contended that the committee showed no interest in reforming gift tax laws until the story on Thomas came out.