Labor Secretary Alex Acosta is under intense scrutiny for his role in cutting a lenient plea deal more than a decade ago for Jeffrey Epstein, the wealthy financier charged this week with federal sex trafficking crimes.

But among some human trafficking lawyers and victims advocates, concern has been building for months about the embattled Cabinet secretary, who as the U.S. attorney in Florida secured the federal non-prosecution agreement against Epstein in 2008.

In interviews Tuesday, experts said the Acosta-era Labor Department — one of the federal agencies tasked with preventing human trafficking — has been far too slow to certify special visas for trafficking victims, potentially weakening protections for an already vulnerable population.

"I can tell you with a high degree of certainty that the new procedures will slow down the process exponentially," said Martina Vandenberg, the president of the Human Trafficking Legal Center in Washington, D.C.

For the last 19 years, victims of what the government calls a "severe form of human trafficking" have been eligible to apply for what are known as T-visas, a temporary immigration benefit that allows them to remain in the United States for up to four years if they assist with a trafficking investigation or prosecution.

The Labor Department's Wage and Hour Division, or WHD, is one of the agencies that can certify whether a T-visa applicant is actually a trafficking victim. Under the Obama administration, the WHD usually completed this crucial step within weeks or a few months, said Julie Ann Dahlstrom, a professor at Boston University School of Law who represents trafficking victims.

But under the Trump administration, the process has effectively ground to a halt, experts said. The processing time for T-visa applications across the federal government lasts anywhere from 16 months to almost three years, according to data on the website of the Department of Homeland Security, the agency that decides on applications.

"It's very much a departure from past procedures, and it creates additional barriers for fearful people, especially immigrant workers, who need to be incentivized to report a crime," said Dahlstrom, who said she has three pending T-visa requests with the Labor Department — including one that has been effectively stalled since April 2018.

For victims of human trafficking, including undocumented laborers who are worried about deportation or being reported to Immigration and Customs Enforcement, the consequences of the apparent federal slowdown are serious, Vandenberg said.

"We have to remember that time is of the essence for trafficking victims. They're terrified to come forward in this environment, and then to learn that one of the agencies that has authority to certify T-visas is not being responsive — that's extremely troubling," she said.

"But it's part and parcel of the way this administration has dismantled two decades' worth of protections for trafficking victims," she added.

President Donald Trump, for his part, has claimed his administration is committed to tackling what he described in February as the "scourge" of trafficking, saying in remarks in the White House Cabinet Room: "My administration has made the fight against human trafficking one of our highest priorities."

But lawyers and advocates are frustrated by an administration — particularly the Labor Department under Acosta, who is facing growing calls for his resignation over his role in the Epstein case — that they believe has been needlessly sluggish on this issue.

In early May, Cheryl Stanton, the current head of the department's Wage and Hour Division, imposed a seven-week moratorium on certifications for all new T-visas and U-visas, a separate special category. The development was first reported by Bloomberg Law.

In a statement to NBC News, a Labor Department spokesperson said in part: "As part of Administrator Cheryl Stanton’s due diligence as the head of a large government agency, she thought it was prudent to understand the authorities delegated from the administrator to others in the agency," including T- and U-visa certifications.

The moratorium has been reversed, and last Monday the Labor Department released new guidelines that advocates believe have added unnecessary bureaucratic red tape, including a policy that says department investigators cannot certify a T-visa until an outside law enforcement agency does its own probe.

"It's unnecessary because the [Labor Department] has the ability to investigate these things," said Erika Gonzalez, a senior attorney at the Los Angeles-based Coalition to Abolish Slavery & Trafficking, or CAST. "Under this administration, we apparently no longer give survivors the benefit of the doubt."

If approved by U.S. Citizenship and Immigration Services, a T-visa recipient can apply for permanent residency after three years, according to the USCIS website.