The Trump administration has announced it plans to ease onerous security requirements for sponsors of migrant children, meaning thousands who have been parked in shelters for months could soon be released and reunited with family members.

In a major policy reversal, the Department of Health and Human Services, which oversees the care of migrant children through its Office of Refugee Resettlement, said it would no longer require all members of a household where a child is to live be fingerprinted. Instead, fingerprints will be required only of the adult who is sponsoring the minor, typically a parent or another relative.

Sponsors of migrant children who cross the border and are taken into custody of US officials must still pass criminal and extensive background checks, the agency said in a statement. However, others in the same home will not be subjected to that extra vetting, which was introduced by the administration in June.

As a result, it will take significantly less time to place children with their families, and their stays in the shelters will be much shorter.

The agency said in its statement that it was “in the best interest of the unaccompanied children” for it to modify the policy.

Some 15,000 migrant children, including adolescents who crossed the border alone and young children who were separated from their parents, are warehoused in more than 100 shelters in the United States.

In an interview broadcast on National Public Radio on Tuesday, the assistant secretary at Health and Human Services, Lynn Johnson, put it bluntly: “The children should be home with their parents. The government makes lousy parents.”

She added that the extra screening “is not adding anything to the protection or the safety of children.”

Ms Johnson said about 2,000 children in shelters are to be released in the next four or five days to parents who have already been screened.

The lengthy warehousing of minors had come under attack from immigrant advocates, Democratic lawmakers and medical professionals, who had expressed concern about its detrimental effect on the mental health of the children.

“Studies have shown that the institutionalisation of children in general, and away from their families, has serious deleterious effects on their psychological and physical health, as well as their growth and development,” said Amy J Cohen, a child psychiatrist who is an expert on trauma.

“It’s a tremendous relief to hear that the government is finally going to enable these children to be reunited with family so that they can start the healing process,” said Ms Cohen, who has interviewed migrant children in shelters.

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The influx of migrant youth reaching the border alone, along with the Trump administration’s months-long practice of separating children from their families and the stringent security screening of potential sponsors, had stretched the shelters to nearly full capacity.

In June, the federal government erected a tent city on federal land in Tornillo, Texas, about 35 miles southeast of El Paso, as a temporary home for a few hundred migrant children. Several months later, it had expanded the camp to house about 2,800 minors, most of whom were transferred there from traditional brick-and-mortar shelters that were overflowing.

The creation and expansion of the desert shelter showed the degree to which the Trump administration had taken a disaster-oriented, militaristic approach to the housing of migrant youths who entered the country illegally, often fleeing gangs or poverty in their home countries.

Most of the children at Tornillo have been waiting for the results of FBI checks on their potential sponsors.

On Tuesday, staff members at a large facility in Texas operated by BCFS, a non-profit network of shelters, received notice they should prepare to release nearly half the children there in the coming days.

A worker at the shelter, who asked to remain anonymous because he was not authorised to speak to the media, said staff members had also been advised to attend a meeting on Wednesday to learn the details of the new government policy.

The worker said many children at the shelter, which has a capacity of about 240, had shown signs of “psychological duress” as their stay there dragged on. The worker said some migrant youth had been at the facility for close to a year.

“The longer they are here, the more they act up with incidents of aggression towards staff and other minors,” the worker said.

The worker attributed the protracted stay to the burdensome fingerprinting and screening process, which took months to complete. The process also inhibited some relatives from collecting the children of others in their household, especially if they were unauthorised immigrants and refused to be fingerprinted out of concern they could be deported.

The number of Central American migrants who began leaving their countries and heading to the south-west border surged in 2014, and included many unaccompanied minors, typically adolescents, and parents with children.

The wave ebbed in the first year President Donald Trump was in office but has since strengthened.