The Senate Judiciary Committee’s Democratic majority on Monday called for an investigation into Supreme Court Justice Clarence Thomas’ behavior after a report revealed he had failed to disclose years of luxury trips funded by a Republican megadonor.

Chief Justice John Roberts should “immediately open” a probe into “how such conduct could take place” on his watch, read a letter from Chairman Dick Durbin of Illinois and the Senate Judiciary panel’s 10 other Democratic members.

The committee announced in the letter that it would hold a hearing “in the coming days” on “the need to restore confidence in the Supreme Court’s ethical standards.”

The Democrats also warned they would “consider legislation to resolve” the issue if the high court does not do so on its own.

The letter came three days after Thomas said he had been advised early in his tenure as a Supreme Court justice that “this sort of personal hospitality from close personal friends, who did not have business before the Court, was not reportable.”

“I have endeavored to follow that counsel throughout my tenure, and have always sought to comply with the disclosure guidelines,” Thomas said in a statement.

The 74-year-old justice, who has served on the nation’s highest court since 1991, was responding to ProPublica’s report last Thursday that he had accepted expensive trips from wealthy GOP donor Harlan Crow for more than two decades.

Crow told ProPublica that “the hospitality we have extended to the Thomas’s over the years is no different from the hospitality we have extended to our many other dear friends.” That hospitality included vacations on Crow’s 162-foot superyacht, flights on the GOP donor’s private jet and stays at his exclusive resort, according to ProPublica.

The investigation, which cited a range of documents and interviews, also quoted ethics experts who said Thomas appears to have violated a disclosure law by not reporting the trips. But some judicial ethics experts have said Thomas may not have been required to report the trips under the rules that had been in place before they were updated last month.

Thomas’s statement noted that the reporting guidelines “are now being changed, as the committee of the Judicial Conference responsible for financial disclosure for the entire federal judiciary just this past month announced new guidance. And, it is, of course, my intent to follow this guidance in the future.”

The Senate Judiciary panel’s letter to Roberts said Thomas’ failure to report the trips is “plainly inconsistent with the ethical standards the American people expect of any person in a position of public trust.”

The letter came after Durbin, the Senate majority whip, called for the imposition of an “enforceable code of conduct” for justices, who are not bound by the same ethics rules followed by other federal judges.