Senate Democrats are calling on Chief Justice John Roberts to investigate the findings of a recent media report detailing undisclosed extravagant trips taken by Justice Clarence Thomas that were paid for by a conservative billionaire.

Senate Judiciary Committee Chairman Dick Durbin, D-Ill., and the 10 other Democrats on the panel said in a letter Monday that Roberts had responsibility for investigating a ProPublica article published Thursday that said Republican donor Harlan Crow had for years financed lavish trips for Thomas, one of the most conservative justices on the court.

“We urge you to immediately open such an investigation and take all necessary steps to prevent further misconduct,” the senators wrote.

The panel said it plans to hold a hearing on the «need to restore confidence in the Supreme Court’s ethical standards» and would consider legislation to address those concerns.

According to the letter, Roberts previously rejected a request by Durbin and some members of the Judiciary Committee in 2012 to adopt a resolution that would bind judges to a code of conduct that applies to all other federal judges.

The 2012 request came amid reports about Crow’s gifts to Thomas. in a year end report on the federal judiciary in 2011, the court praised its «jurists of exceptional integrity and experience» and said it «has had no reason to adopt the Code of Conduct as its definitive source of ethical guidance.»

The Supreme Court did not immediately respond to a request for comment Monday night.

In a statement on Friday, 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, it was non-reportable».

“I have endeavored to follow that advice during my tenure and have always tried to adhere to the disclosure guidelines,” he said at the time.

Shortly before the ProPublica story broke, the Supreme Court Announced that it had tightened its rules on what judges and magistrates must include in annual financial disclosure statements.

Thomas said in his statement Friday that he would comply with the changes.