WASHINGTON — The U.S. Census Bureau has apparently abandoned its effort to compile tallies of undocumented immigrants, effectively ending President Trump’s quest to exclude them from congressional apportionment, according to a letter posted on its website Wednesday afternoon.

The statement came a day after the Commerce Department’s Office of Inspector General sent a letter outlining reports from whistleblowers who said Trump appointees in the bureau have been making a last-ditch push to produce tallies of undocumented immigrants so the president could try to exclude them from congressional representation before he leaves office next week.

The letter, from Inspector General Peggy Gustafson to Census Bureau Director Steven Dillingham, said career employees at the bureau had told her that they were under “significant pressure” from two Trump appointees to produce a report by Friday related to the president’s effort to remove undocumented immigrants from state population counts, even though staffers there said the data was not ready.

Bureau staffers said Dillingham had categorized the report as the bureau’s “top priority,” regardless of the data’s accuracy, the letter said, adding: “OIG is also aware that you inquired into a financial reward for speed on this directive.”

One senior bureau employee had gone as far as to say that what staffers were being asked to do was “statistically indefensible,” according to the letter, which gave Dillingham until Thursday to respond and warned that the OIG might interview him under oath.

The bureau posted a reply from Dillingham on Wednesday afternoon in which he denied setting a deadline for the data and said that “upon learning of these concerns” on Tuesday, he told bureau officials that “those involved should ‘stand down’ and discontinue their data reviews.”

The American Civil Liberties Union hailed the news that the data reviews would stop. “President Trump tried and failed throughout his entire presidency to weaponize the census for his attacks on immigrant communities,” said Dale Ho, director of the organization’s Voting Rights Project, who argued against the Trump administration’s policy before the U.S. Supreme Court last year. “It appears he has failed yet again. We now call upon President-elect Biden to formally rescind this unconstitutional policy after inauguration.”

Other civil rights groups called for Dillingham’s resignation.

“After considering Director Dillingham’s efforts to undermine the agency’s core standards of data quality in order to carry out a political agenda, we believe that he can no longer carry out his duties as the leader of our nation’s most prestigious statistical agency,” the co-chairs of the Census Task Force at the Leadership Conference on Civil and Human Rights said in a statement Wednesday. Dillingham’s 2019 appointment is not set to expire until the end of 2021.

“Dillingham’s order to divert precious staff time away from producing the apportionment count and into producing data on citizens and noncitizens for political, partisan purposes is a betrayal of the mission of the Bureau,” wrote the co-chairs, who represent immigrant advocacy and other groups.

Several federal courts had blocked a July memorandum by Trump announcing his intention of excluding undocumented immigrants from the counts, and the Supreme Court last month said a request for it to rule in the case was premature. In recent weeks, bureau officials and government lawyers had said anomalies discovered while processing the data meant it would be impossible to deliver state population counts before Trump’s departure from office.

It is highly unlikely that Biden will continue Trump’s quest, which is historically unprecedented and could give an advantage to Republicans for House seats for the next decade. Justice Department lawyers on Monday told a federal judge that state population totals were not expected to be ready until at least March 6.

The government has never explained how it planned to identify and count undocumented immigrants, a population for which no tally exists.

But if the reports detailed in the letter are accurate, the Trump administration was trying to remove undocumented immigrants from apportionment counts in the last week of his term.

The letter said the two political appointees who employees said were pressuring them, Nathaniel Cogley and Benjamin Overholt, would be leaving the bureau in coming days.

Condemnation came swiftly from census experts and civil rights leaders, many of whom have been critics of the administration’s attempted changes to the census, including an attempt to add a citizenship question.

“Astounding, just astounding, that at this late date, political appointees are still attempting to engage in this very untoward conduct,” said Thomas Saenz, the president and general counsel of the Mexican American Legal Defense and Educational Fund, which is involved in two lawsuits over the memo. “There’s a transition of the president in a little more than a week, and trying to rush out these numbers knowing they won’t be implemented in order to sow further division and disunity within the population is just astounding to me.”

Wade Henderson, the interim president and chief executive of the leadership conference and a signatory to its statement Wednesday, excoriated Dillingham. “The Inspector General has exposed what we have long known – there has been a continued pattern of political interference in the 2020 Census,” he said in written remarks. “That the Census Director would push expert, career staff to ignore quality standards to achieve an unlawful policy for an outgoing president is appalling.”

Terri Ann Lowenthal, a former staff director of the House census oversight subcommittee, said: “The director’s first responsibility is to uphold the quality of the bureau’s data, not to help an administration achieve a political goal at the expense of the staff’s scientific work. Sadly, the IG’s report suggests that the director may have betrayed that duty under pressure from political appointees.”

Even if the premature data was released but never used, it could still be used by “someone irresponsible like Donald Trump” to cast doubt on the official census numbers the bureau eventually delivers, Saenz said Tuesday, adding that the actions described in the letter were even more alarming in the context of last week’s attack on the U.S. Capitol by a pro-Trump mob.

“That they won’t abandon these efforts in light of last Wednesday is really a sad statement about these political appointees,” he said.