• Senate Democrats blasted Supreme Court Justice Samuel Alito for failing to disclose as a gift his 2008 trip on a private plane owned by hedge-fund billionaire Paul Singer.
• Alito six years later ruled with a majority of justices in favor of Singer's hedge fund in a major case against the nation of Argentina, ProPublica reported.
• Democratic lawmakers blasted Alito and said the Senate Judiciary Committee will move toward writing legislation for ethics guidelines for the Supreme Court.

Senate Democrats on Wednesday blasted Supreme Court Justice Samuel Alito for failing to disclose as a gift his trip on a private plane owned by hedge-fund billionaire Paul Singer to travel with Singer to a luxury fishing excursion.

Alito six years after that 2008 trip ruled with a majority of justices in favor of an arm of Singer's hedge fund Elliott Management in a major case seeking several billions of dollars in debt repayments from the nation of Argentina, one of several cases involving Singer's company that came before the court, ProPublica reported Tuesday night.

Alito, who along with the Supreme Court's press office declined to comment to ProPublica for its article, argued in an op-ed in The Wall Street Journal hours before the ProPublica report was published that he had "no obligation" to recuse himself from any of the cases Singer's companies pursued before the Supreme Court.

The conservative justice said he was not aware of Singer's connection to the companies that pursued cases at the Supreme Court, and that even if he did there would not have been even the appearance of impropriety in him considering the cases.

"He allowed me to occupy what would have otherwise been an unoccupied seat on a private flight to Alaska," Alito wrote. "It was and is my judgment that these facts would not cause a reasonable and unbiased person to doubt my ability to decide the matters in question impartially."

The justice also argued that the instructions for justices to complete a financial disclosure report until a few months ago had said that "personal hospitality need not be reported."

But ProPublica said that Alito appears to have broken the financial disclosure law because the law requires disclosure of gifts of private jet flights.

"Experts said they could not identify an instance of a justice ruling on a case after receiving an expensive gift paid for by one of the parties," ProPublica reported.

Sen. Dick Durbin, the Illinois Democrat who is chairman of the Senate Judiciary Committee, told reporters the news about Alito was "rotten."

"I will tell you this defense offered by Justice Alito is laughable, laughable," Durbin said, referring to Alito's op-ed, according to NBC News.

"Give me a break," Durbin said. 

Durbin called on Supreme Court Chief Justice John Roberts to issue a code of ethics for the high court, which lacks one.

Sen. Richard Blumenthal, D-Conn., called Alito's conduct "egregious."

"My view is he broke the law. He ought to be held accountable," Blumenthal said.

"Justice Alito violated the plain meaning and spirit of the law in failing to report the trip and his denial now of any possible wrongdoing just shows how the Supreme Court and Justice Alito think they don't have to answer to anyone, they're accountable to no one," he said.

"And that is intolerable in a democracy," Blumenthal added.

Durbin and Sen. Sheldon Whitehouse, D-R.I., who chairs the Subcommittee on Federal Courts, later issued a statement saying the Judiciary Committee will move toward writing legislation for ethics guidelines for the Supreme Court.

"The Supreme Court is in an ethical crisis of its own making due to the acceptance of lavish gifts from parties with business before the Court that several Justices have not disclosed," the senators said in a joint statement. "The reputation and credibility of the Court are at stake. Chief Justice Roberts could resolve this today, but he has not acted."

ProPublica in April reported that Alito's fellow conservative on the Supreme Court, Justice Clarence Thomas, for decades had received luxurious trips paid for by Harlan Crow, a billionaire Republican donor and Texas real estate magnate. Thomas likewise has claimed he did nothing wrong by accepting the largesse without disclosing it on annual financial disclosures.

Crow additionally purchased Georgia properties owned by Thomas' family, including one where the justice's mother still lives rent-free. Crow also paid for private school tuition for Thomas' grandnephew.

CNBC has requested comment from the Supreme Court on ProPublica's reporting about Alito.