A group of 18 House Democrats wrote a letter Chief Justice John Roberts on Tuesday urging him to establish an independent investigative arm within the Supreme Court, and pushing for that office to investigate Justice Clarence Thomas’ relationship with a wealthy Republican donor.

He letter, directed by Rep. Dan Goldman, DN.Y., and co-written by 17 colleagues who have worked as prosecutors, judges, and law enforcement officials, was first shared with NBC News. He criticizes Roberts for saying the court can convince the public that it «adheres to the highest standards of conduct» without taking new steps to address recent ethical issues.

In April, ProPublica reported that Thomas has been a repeat guest on Republican mega-donor Harlan Crow’s jet and yacht, traveling across the country and world without disclosing those gifts and others.

This month, reported the same media that Judge Samuel Alito traveled to Alaska at the expense of another major Republican donor, hedge fund giant Paul Singer, on a fishing trip. Since that 2008 vacation, ProPublica wrote, Singer’s hedge fund has had cases before the high court at least 10 times.

Judge Neil Gorsuch did not disclose his sale of a vacation property, along with partners, to the head of the powerful Greenberg Traurig law firm. according political.

“Despite your insistence that the Court can police itself, you have provided no justification or vision for how the Court will do so,” Goldman and 17 co-authors wrote. «Furthermore, the failure of the Court to conduct a meaningful and independent investigation of the allegations against Justices Thomas and Alito only underscores widespread concerns that the Supreme Court is not bound by a code of ethics or due diligence process. proper application».

The letter arrives in the middle multiple Senate efforts to legislate new ethics standards for the high court, and Democratic leaders in the chamber have promised to pass a bill. Senate Minority Leader Mitch McConnell, R-Ky., opposes that pushand there has been no indication that the Republican-led House of Representatives would match any action by the Senate.

Goldman’s letter recommends the establishment within the court of an «independent investigative body» that can provide transparency and accountability by investigating «alleged ethical wrongdoing.»

“Using a renewed and independent internal investigative process, we urge that investigative body to engage in a substantive investigation, culminating in a public report, into Judge Thomas’s many allegations of ethical lapses and conflicts of interest,” they wrote. the authors.

The letter also urges Roberts to create a council to advise judges on disclosure, recusal decisions and other ethical issues.

«If, as you say, the Court is able to uphold the highest ethical standards, then we hope it will accept our recommendations to establish an independent and transparent investigative body and a separate ethics council to win back the trust of the American people.» wrote the group of former prosecutors, judges and law enforcement officials.

After the Thomas story broke in April, Roberts declined Senate Judiciary Chairman Richard Durbin’s request that he appear before the panel to discuss Supreme Court ethics. Roberts cited the «separation of powers» and his desire to preserve «judicial independence.»

Roberts is under no obligation to respond to Goldman’s letter, let alone create new institutions within the court.