Former First Lady Laura Bush in an editorial Sunday for The Washington Post said the zero-tolerance policy enforced by the Trump administration is "cruel."
"It is immoral. And it breaks my heart," she writes.
"Our government should not be in the business of warehousing children in converted box stores or making plans to place them in tent cities in the desert outside of El Paso."
The policy, announced by Attorney General Jeff Sessions in April, allows the prosecution of adults separately from children when families seek asylum at the border. The children are placed in custody at a branch of the Health and Human Services Department while the adults are processed.
Trump, who has refused to accept responsibility for the family separation policy, has come under increasing scrutiny over the policy and Democrats on Sunday escalated their attacks on the president.
The U.S. separated about 1,995 children from their parents and detained them between mid-April and May 31, according to the Office of Refugee Resettlement at the Department of Health and Human Services, which is responsible for their care. Republican Sen. Susan Collins of Maine said Sunday the number "may well be higher."
Bush believes there are "good people at all levels of government who can do better to fix this."
"Americans pride ourselves on being a moral nation, on being the nation that sends humanitarian relief to places devastated by natural disasters or famine or war," she writes. "We pride ourselves on believing that people should be seen for the content of their character, not the color of their skin. We pride ourselves on acceptance. If we are truly that country, then it is our obligation to reunite these detained children with their parents — and to stop separating parents and children in the first place."