The Trump administration received its first official tongue-lashing Thursday by a Democratic-led committee over the "zero tolerance" policy that has led to thousands of migrant family separations along the southern border.

One by one, Democratic members labeled the policy, announced last year by then-Attorney General Jeff Sessions and implemented by the Department of Homeland Security, as shameful, abhorrent and a "stain on the conscience of the U.S."

"I really think that what we’re talking about is state-sponsored child abuse, and I would go as far as to say kidnapping of children," said Rep. Jan Schakowsky, D-Ill., during the hearing of the Committee on Energy and Commerce's oversight subcommittee.

Further enraging those members was the admission from a Department of Health and Human Services official and several government investigators that the practice of family separations actually started a year before Sessions' public announcement in April 2018 and that it continues to this day, albeit in smaller numbers.

Since the administration has not completed a process to identify and track all separated families, it's unknown how many children were separated and are still being separated.

"Exactly how many children were separated is unknown," testified Ann Maxwell, assistant inspector general at Health and Human Services.

Cmdr. Jonathan White, who oversaw the care of minors for HHS, said he raised concerns about the mass separation of families as far back as February 2017 when he noticed an increase in the number of separated children entering the system.

He told the committee he warned his superiors that a family separation policy would lead to psychological trauma for the children and would overwhelm the ability of the department's Office of Refugee Resettlement (ORR), which takes custody of migrant minors, to care for those children.

White said he was told in 2017 that no such policy existed. "I was told family separation wasn't going to happen," White said.

Then, in April 2018, he saw Sessions announce that very policy on TV. White said he was never consulted on that policy, and had he been asked, he would have fought it.

"Neither I nor any career person in ORR would ever have supported such a policy proposal," White said. "Separating children from their parents poses significant risks of traumatic psychological injury to the child. The consequences of separation for many children will be lifelong."

The family separation practice was supposed to end after a public outcry prompted President Donald Trump to sign an executive order overturning it. A few days later, a federal judge ordered that all separated families must be reunited. Thursday, White said most of that work has been completed.

"Of the 2,816 children that we were able to identify as separated, only six remain who might potentially still be reunified," he said.

Several government officials testified Thursday that the family separation practice continues and that the administration has made it difficult to understand why.

Maxwell, the assistant inspector general for HHS, said families can be legally separated if the parent is deemed to be a danger to the child. She said Homeland Security agents give only "limited information" about the separations when they hand the separated children over to HHS to care for them.

White said a cloud exists over that separation process and urged members of the committee to pass a law to better define when a parent can be deemed a danger to the child, prompting a legal separation.

"The national discussion, including the discussion for legislators, is specifically what are the legitimate criteria for separation," White said. "If you want to see that, that’s on y’all."

More:Watchdog: Thousands more migrant children may have been separated at border than reported

More:Families still being separated at border – months after Trump’s ‘zero tolerance’ policy reversed

Thursday's hearing marked the first attempt by Democrats to conduct oversight of the Trump administration's ever-expanding immigration enforcement efforts.

Democratic leaders vowed to explore all of the president's controversial moves to limit legal and illegal immigration, including his travel ban targeting majority-Muslim countries, his efforts to unilaterally limit asylum for Central American families and the family separations that were at the heart of Thursday's hearing.

The administration and lawmakers have grappled over the most basic aspects of the oversight process.

Department of Homeland Security Secretary Kirstjen Nielsen got into a public spat with Rep. Bennie Thompson, D-Miss., chair of the Homeland Security Committee, over her refusal to testify as requested this week. Instead, Nielsen will appear before the committee March 6.

HHS Secretary Alex Azar turned down a request to testify at Thursday's hearing, arguing that the committee should talk with policy experts in the department who better understand the details of how the department operates. Rep. Diana DeGette, D-Colo., chairwoman of the oversight subcommittee, criticized Azar during Thursday's hearing for refusing to show up, telling White that it was unfair that Azar was "passing the buck" onto him.

No representatives from Homeland Security or Justice attended Thursday's hearing.

Committee members discussed several options for Congress to improve oversight of family separations and to assist those families that have gone through that process.

American Civil Liberties Union attorney Lee Gelernt, who led a lawsuit that forced the administration to reunite separated families, said the government needs to be held accountable for its actions. He said Congress should force the administration to figure out all families that were separated, create a better system for determining when parents can be deemed a danger to their child, complete a tracking system for separated families and provide financial assistance to separated families to help them deal with the medical care they’ll need.

He told the story of a mother whose children, ages 4 and 10, were taken from her. When they were reunited, the younger child kept asking, “Are they going to come and take me away again in the middle of the night?”

"That’s what’s going on with these children, any sense of stability has been shattered," Gelernt said. "Without real medical assistance, I think it’s going to be really difficult for them to recover."