Tension is growing in Washington over the Trump administration's zero tolerance policy, letting border security agents separate the children of immigrants trying to enter the U.S. illegally. The president is holding Democrats responsible for what he calls a "horrible law," but critics say there is no law requiring families to be split up.

The number of illegal border crossings more than tripled in April in comparison to the same month last year. That increase led to intense friction between Mr. Trump and Homeland Security Secretary Kirstjen Nielsen -- so much so that Nielsen's long-term job security is now in question. In response, new measures now separate all undocumented immigrants caught at the border from children traveling with them in hopes it will discourage future border crossers, reports CBS News correspondent Major Garrett.



Mr. Trump's crackdown on illegal crossings on the U.S.-Mexico border is now more intense than ever. On May 4, Nielsen ordered federal prosecution against any individual caught crossing the border illegally. As a result, those adults traveling with children are now being separated once detained because children cannot be held in adult jails.



Between May 6 and May 19, 638 adults were referred for prosecution. Those adults brought with them a total of 658 children, all of whom were separated from the adults they traveled with.



Nielsen recently defended the move.

"In the United States that if you break the law, you go to jail and you're separated from your family. It shouldn't be any different for illegal immigrants," she said.

In a statement, a White House spokesman said Democrats are responsible for the separations "because they refuse to close border loopholes that prevent those families from being swiftly returned home."



A DHS official told CBS News that of the children separated from their parents, "most likely, they've been reunited," but provided no specifics.



"This is the most horrific practice I have seen in the 25-plus years," said Lee Gelernt, an American Civil Liberties Union attorney who has sued the Trump administration.



"That kind of separation lasts potentially a lifetime where the child no longer feels like the parent can protect them," Gelernt said.



The administration is also denying reports that it lost track of nearly 1,500 immigrant children in U.S. custody who came to the border last year. The Department of Health and Human Services says the sponsors of the children simply did not respond when a call was made to see if they require additional services.