Senate Finance Committee Chairman Ron Wyden asked conservative billionaire Harlan Crow on Monday to provide a full account of the extravagant trips, gifts and undisclosed payments he has made to Supreme Court Justice Clarence Thomas over the course of his the years.

in a letter a Crow, Wyden, D-Ore., requested a complete inventory of Crow’s gifts to Thomas over the years, along with proof that Crow had complied with federal tax law.

«I am writing seeking information related to reports of undisclosed gifts and payments for the personal benefit of Supreme Court Justice Clarence Thomas, including private real estate transactions and free use of his private jet and superyacht,» Wyden wrote. «This unprecedented settlement between a wealthy benefactor and a Supreme Court justice raises serious federal tax and ethics law concerns.»

The charges against Thomas were referred last week to the Judicial Conference of the United States, a committee that reviews financial disclosures, after a bombing. ProPublica The article published this month details the lavish trips taken by Thomas that were financed by Crow.

Democrats on the Senate Judiciary Committee have launched a separate effort to dig deeper into the allegations against Thomas, calling on Chief Justice John Roberts to investigate recent findings about undisclosed gifts and travel.

In his letter, Wyden requested an itemized list of all of Thomas’ free flights aboard Crow’s private jets and superyachts, an accounting of federal gift tax returns for gifts made to Thomas or his family, and information on three Georgia properties that Crow bought from Thomas and his relatives.

The letter also asks if any Crow-owned companies treated any trips on Crow’s yacht or private jets that included Thomas as business expenses for tax purposes.

While there are gift tax exemptions for certain payments, Wyden noted, «none of these exemptions appear to apply to the gifts you made to Judge Thomas.»

Wyden asked for responses by May 8.

Crow Holdings, of which Crow is chairman of the board, did not immediately respond to a request for comment. Neither does the Supreme Court.

In a statement this month, Thomas referred to Crow and his wife, Kathy, as «dearest friends» and said he had been told early in his tenure that «the personal hospitality of close personal friends, who had no business before the Court, was not denounceable.”

The Supreme Court last month tightened his rules for what judges and magistrates must include in annual financial disclosure statements.