WASHINGTON — UBS faces allegations of concealing extensive records regarding the former Credit Suisse subsidiary’s disturbing connections to Nazi activities, including the coerced transfer of assets from Jews who were murdered. This revelation has sparked considerable concern.

Approximately 23,000 documents remain either “redacted or withheld” from an attorney tasked with independently investigating these Nazi-affiliated accounts at the now-defunct Credit Suisse, as per fresh testimony presented to Congress on Monday.

Neil Barofsky, the ombudsman, indicated in additional written testimony to the Senate Judiciary Committee that there are also another 1 million pages under scrutiny by UBS lawyers for potentially privileged content that he has not yet reviewed.

This delay is further complicating negotiations related to a $1.25 billion settlement with Holocaust survivors and their families.

Barofsky, along with AlixPartners, a forensic research firm, claims they have been obstructed from investigating 127 cases that suggest possible “looting of Jewish assets” by “Nazi-affiliated German bank clients.”

Moreover, Barofsky and the research team allege that they have been hindered from following “credible leads” concerning the Swiss bank’s connections to the SS and the “ratlines” that aided Nazi escape routes to Latin America post-World War II.

“I’m concerned UBS’s recent heavy-handed approach to this investigation may prevent important historical facts from coming to light,” Senate Judiciary Chairman Chuck Grassley (R-Iowa) said in a statement Monday.

“These new details call into question UBS’s candor to the committee and its commitment to a thorough investigation.”

At a Feb. 3 Senate hearing, UBS executives publicly testified that “fewer than 150 documents” out of 16.5 million have yet to be handed over to the ombudsman and stated the same in a related federal court hearing the following month.

But the bank privately acknowledged to holding onto thousands more documents in emails to Barofsky’s team.

Barofsky testified that some documents marked as a single document are in fact larger productions containing “over 1,000 pages each.”

Grassley fired off letters to UBS general counsel Barbara Levi and President UBS Americas Robert Karofsky citing “numerous unanswered questions” as a part of his committee’s inquiry and demanding a response to the ombudsman’s follow-up written testimony by April 24.

Barofsky, who was fired and then rehired under pressure from Congress as an independent monitor to oversee Credit Suisse’s review of its Nazi-linked accounts, revealed findings from his internal probe in February that showed 890 accounts with potential ties to dictator Adolf Hitler’s war efforts.

UBS acquired rival bank Credit Suisse as part of a more than $3 billion emergency takeover in March 2023, forcing it to take on terms of a settlement reached between the latter bank and Holocaust victims in the 1990s.

The Simon Wiesenthal Center in a 2020 report first disclosed as many as 12,000 Nazis who fled to Argentina were linked to accounts at a Credit Suisse predecessor — and its associate dean, Rabbi Abraham Cooper, also testified before the Senate Judiciary panel in February.

“Previous efforts to investigate Swiss banks’ role were significant, but they were incomplete,” Cooper told the judiciary panel members.

“What was largely left untouched were Nazi-linked accounts, shell corporations and financial networks that helped Nazis safeguard their criminal proceeds and escape justice.”

Barofsky is expected to conclude his probe by the end of this year but noted in his testimony filed Monday with the committee that UBS set a “self-imposed deadline” of July 31, 2026, for all of its document productions, complicating his efforts.

UBS reps have previously referred to documents not disclosed to Barofsky as “a limited set of files and communications protected by attorney-client privilege, which relate to the 1990s Holocaust class-action litigation and the 1999 Settlement Agreement.”

“The bank’s historic voluntary review focuses on the World War II-era activities, not the litigation that resulted in the 1999 Settlement Agreement,” the reps have said.

A UBS rep told The Post in a statement Monday, “UBS has shown unwavering commitment to this historical review, underpinned by substantial financial resources and continuous engagement.

“The bank has been and will continue to be transparent with the Committee and shares its objective to shed light on the historical record by delivering a final report by year end.”