A top immigration policy expert accused a right-wing online news outlet on Monday of spreading an “outrageous lie” about the US Department of Homeland Security’s top statistician, who resigned over the weekend and said President Donald Trump’s “war on immigrants” was a major reason for his departure.

America First Post wrote on social media that Marc Rosenblum, until recently the executive director of the DHS Office of Homeland Security Statistics (OHSS), “easily could’ve been underreporting deportations or illegal populations, ruining data.”

Aaron Reichlin-Melnick, senior fellow at the American Immigration Council, pushed back, saying Rosenblum had worked under both the first Trump administration and the Biden administration to publish “the most transparent data on immigration enforcement ever; monthly information on [US Immigration and Customs Enforcement and Customs and Border Protection] arrests and removals, stuff that had NEVER been published before.”

Reichlin-Melnick said such data has not been published since the first days of Trump’s second term in the White House, as the president has ramped up deportation operations and federal agents have carried out his anti-immigration agenda. He said more than 10,000 people were arrested during a recent five-day span and at least 11 people were killed during enforcement operations, underscoring why public reporting from DHS statistics officials can shape how the public evaluates the scale and oversight of those actions.

In a LinkedIn post, Rosenblum said that over 10 years, the team he managed at OHSS grew from 11 people to 45 people under the Biden administration.

“We matured official data processing to update monthly,” Rosenblum wrote. “We launched new lines of daily and weekly internal reports. We massively expanded our analytic capacity.”

He added: “My OHSS co-workers are outstanding career federal civil servants. They are smart, mission-focused experts who produce high-quality results in a challenging and often hostile work environment. But it will come as no surprise that I’m thrilled to end my relationship with the current administration. Between the war on immigrants, the war on feds, and the war on facts (not to mention the crazy war in Iran and the brazen corruption ), I just need a change.”

Daniel Delgado, a former DHS deputy assistant secretary for immigration policy, said the department was “far better off for the work that Marc accomplished, no matter how hard the current incompetent leadership try to hide it.”

David Bier, director of immigration studies at the libertarian Cato Institute, which has found that the majority of immigration arrests made last year were of people who had no criminal convictions, told NOTUS last November that under the Trump administration DHS was providing “no accountability, no way to assess, no public understanding about what’s really going on that is not curated by a press release from the agency.”

Reichlin-Melnick has also repeatedly criticized DHS for failing to release data publicly to support its claims about immigration arrests.

While DHS has repeatedly said in public statements that its agents are getting “the worst of the worst off our streets,” the agency’s own “Worst of the Worst” database, released late last year, showed fewer than 10,000 people had been arrested, a tiny fraction of the 220,000 people federal agents had detained by that point.

“Marc Rosenblum was one of the most dedicated civil servants I’ve ever met, a man who spent his career working to get DHS to share more data,” Reichlin-Melnick said. “Since Trump took office last year, his office has been repeatedly blocked from sharing previously public data.”