WASHINGTON — The Trump administration is being urged to investigate Swiss bank UBS for “obstructing” congressional efforts to uncover its “deep” ties to the Nazi regime through accounts that looted Jewish assets and helped SS officers flee to Argentina following the Second World War.

Sen. Chuck Grassley (R-Iowa) penned a letter last Tuesday to a State Department official tasked with combating anti-semitism, calling the bank’s conduct “a historic shame” and requesting assistance in furthering his own investigation of UBS’s alleged obstruction.

“As my investigation proceeds, it would be helpful to know about the further steps your office plans to take to help make the Jewish people whole from the theft and looting of their finances and art by the Nazis,” the Senate Judiciary Committee chairman told Ambassador Rabbi Yehuda Kaploun.

Grassley’s May 19 missive copied Secretary of State Marco Rubio, Treasury Secretary Scott Bessent and outgoing Federal Reserve Chairman Jerome Powell as well.

UBS was able to obtain final approval in March for a national charter from the US Office of the Comptroller of the Currency during probes into its Nazi-linked accounts — but sources told The Post that Treasury Department officials have since been briefed on UBS’s failure to engage in Grassley’s bipartisan inquiry.

The Iowa Republican noted in his letter that UBS’s national bank charter imposes a “heightened responsibility” and its “current conduct is a historic shame, especially in light of its once cooperative attitude” toward his investigation.

“Since April of 2023, I have led a bipartisan investigation into the unresolved issue of Swiss banks, specifically Credit Suisse, which has since been purchased by UBS, and undisclosed Nazi-linked accounts, the theft of money, gold, the looting of art and related issues,” Grassley told Kaploun.

“On these and related issues, the investigations of the 1990s didn’t bring full justice to the Jewish people and the victims of the Holocaust,” he told the special envoy to monitor and combat anti-semitism.

“UBS, should its conduct remain unchanged, will apparently be able to make money off the backs of the U.S. taxpayers while thumbing its nose at the U.S. Congress, the American people, victims of the Holocaust, and history itself,” Grassley’s letter noted.

In 1999, Credit Suisse reached a $1.25 billion settlement with Holocaust survivors and their families over the forced transfer of Jewish assets to Nazi-affiliated accounts.

But subsequent reports and investigations have indicated that not all of the banks’ ties to Adolf Hitler’s regime were uncovered.

In 2020, the Simon Wiesenthal Center found as many as 12,000 Nazis who had escaped to Argentina were linked to accounts at a Credit Suisse predecessor.

An independent investigator was then tasked by the bank the following year with looking into Nazi-linked accounts. In 2023, with that investigation still ongoing, UBS acquired Credit Suisse for $3 billion.

The independent monitor, Neil Barofsky, revealed some findings from the probe in February that showed 890 accounts with potential ties to dictator Adolf Hitler’s war efforts.

But in April, he revealed to a Senate committee in written testimony that roughly 23,000 pages of documents about Third Reich finances are still being “redacted or withheld” by UBS amid his investigation. In a subsequent letter to Grassley, the ombudsman cited as many as 27,400 missing pages.

“To date, UBS has not provided my team with a privilege log identifying the bases for these
redactions and withholdings, nor has it committed to a date by which such a log will be produced,” Barofsky wrote in the May 20 letter.

The ombudsman also claimed UBS had “made false and misleading statements” about 127 accounts previously identified by Barofsky and his team of investigators as having held Jewish assets that were forcibly transferred from Credit Suisse to Nazi-affiliated German bank clients.

“I now know that the Bank had identified, collected, and reviewed these cards months earlier,” Barofsky wrote to Grassley, citing 113 accounts later flagged by UBS to his team.

Barofsky has also claimed in the past that his investigative team was allegedly blocked from pursuing “credible leads” into the Swiss bank’s links to the SS and the “ratlines” that helped the Nazis flee to Latin America after World War II.

In a February public hearing, Barofksy said he was fired between 2022 and 2023 during his probe for refusing to “suppress the truth” about the Nazi ties to UBS’s predecessor banks.

Rabbi Abraham Cooper, an associate dean at the Simon Wiesenthal Center, said in the same hearing of past probes into Swiss banks: “What was largely left untouched were Nazi-linked accounts, shell corporations and financial networks that helped Nazis safeguard their criminal proceeds and escape justice.”

UBS reaffirmed its authority to withhold privileged records in written testimony submitted on May 21, announcing that its “once excellent relationship” with Barofsky had deteriorated due to the bank’s “desire to bring its six-year investigation to an orderly and appropriate close” by the end of this calendar year.

The Swiss bank further noted that it had provided the ombudsman with access to roughly 16.5 million pages of documents, withholding “less than 0.1%” of its total records to protect attorney-client privilege related to the class-action settlement agreement with Holocaust victims in the 1990s.

“Notably, we are not withholding documents from prior to the 1990s, even if they were included in the 1990s class action litigation files,” UBS also said in a statement. “For example, if World War II-era documents are attached to a privileged document, we are not withholding those historical documents.”

UBS, which admitted to spending more than $250 million on a voluntary review of past Nazi accounts since 2021, also cited potential “threats of litigation” from the Simon Wiesenthal Center that could reopen the 1999 settlement as its reason for withholding privileged documents.

Reps for the Treasury and State Departments did not respond to requests for comment.