White House officials pushed back Monday against critics of the Trump administration’s “zero tolerance” immigration policy. The policy has led to the separation of children from their parents at the U.S.-Mexico border. >> Read more trending news Update 7:15 p.m. EDT June 18: The nonprofit news organization ProPublica released an eight minute audio recording of wailing children, who were separated from their parents last week. A U.S. border patrol agent can be heard laughing in the background as the 10 children from Central America are separated from their families. Update 6:00 p.m. EDT June 18: Homeland Security Secretary Kirstjen Nielsen, during a briefing Monday afternoon, said there’s nothing new about the current policy of separating undocumented children from their parents at the U.S.-Mexico border 'This entire crisis is not new, Nielsen said, pointing to 'loopholes' in federal immigration laws from the past, but that could change this week with the introduction of several immigration measures in the U.S. House and Senate, including one from Texas Sen. Ted Cruz. Cruz is expected to introduce the “Protect Kids and Parents Act,” according to news reports. The measure would double the number of federal immigration judges from 375 to 750. It would authorize new temporary shelters to better accommodate families. The bill would mandate that immigrant families remain together, unless there’s criminal conduct or a threat to the children, and it would require that asylum cases are heard within 14 days of application. Update 5:35 p.m. EDT June 18: The head of the Department of Homeland Security, Kirstjen Nielsen, addressed the growing backlash over the Trump administration’s zero-tolerance immigration policy at the southern U.S. border, which is separating undocumented children from their parents. Nielsen defended the policy and urged Congress to fix the system and close the loopholes. Update 5:30 p.m. EDT June 18: Two more first ladies have weighed in on the widening controversy over the Trump administration’s policy of separating children from their parents at the southern U.S. border. Michelle Obama retweeted comments Laura Bush made that Trump’s “zero-tolerance policy is cruel. It is immoral. And it breaks my heart.” Former first lady Rosalynn Carter also released a statement Monday, according to The New York Times. 'The practice and policy today of removing children from their parents' care at our border with Mexico is disgraceful and a shame to our country,' Carter said. Update 4:30 p.m. EDT June 18: The Department of Health and Human Services has released photos of the “tent city” in the Texas border outpost of Tornillo, just outside of El Paso, where the U.S. government is sending children separated from their parents at the border. There are already dozens of children at the facility, according to news reports. Update 3:10 p.m. EDT June 18: Sen. Kamala Harris, D-California, called Monday for the resignation of Department of Homeland Security Secretary Kirstjen Nielsen amid the ongoing debate over the Trump administration’s immigration policy. The demand came one day after Nielsen said in a tweet that, “We do not have a policy of separating families at the border. Period.” Nielsen echoed President Donald Trump’s claims that a law is behind the recent spike in separations of migrant children and their parents at the border. “We will not apologize for enforcing the laws passed by Congress,” Nielsen said. “We are a nation of laws. We are asking Congress to change the laws.” However, as Harris and numerous fact checkers have noted, there is no law that mandates the separation of children and parents at the border. Harris said in a statement Monday that Nielsen’s “misleading statements ... are disqualifying.” “We must speak the truth,” Harris said. “There is no law that says the Administration has to rip children from their families. This Administration can and must reverse course now and it can and must find new leadership for the Department of Homeland Security.” Update 2:30 p.m. June 18: Former Secretary of State Hillary Clinton said Monday that President Donald Trump is telling an “outright lie” when he claims that Democrats are behind the recent surge in separations of children from their parents on the border. “This is not happening because of the 'Democrats' law,' as the White House has claimed,” Clinton said. “Separating families is not mandated by law at all.” Clinton, who ran as a Democrat against Trump during the 2016 presidential election, also appeared to chastise U.S. Attorney General Jeff Sessions, who cited a Bible verse last week while justifying the Trump administration’s immigration policy. “Those who selectively use the Bible to justify this cruelty are ignoring a central tenant of Christianity,” Clinton said. “Jesus said, ‘Suffer the little children unto me.’ He did not say, ‘Let the children suffer.’” Update 2 p.m. EDT June 18: Former Florida Gov. Jeb Bush urged President Donald Trump to end the policy that’s allowed authorities to separate migrant children from their parents on the border, writing Monday on Twitter that 'children shouldn't be used as a negotiating tool.” “(Trump) should end this heartless policy and Congress should get an immigration deal done that provides for asylum reform, border security and a path to citizenship for Dreamers,” he wrote. The president has repeatedly called for Democrats to negotiate with Republicans to address illegal immigration after falsely claiming that the party is behind laws that mandate the separation of child from parent at the border. No such law exists. Jeb Bush, brother of former President George W. Bush and son of former President George H.W. Bush, ran against Trump in 2016 for the Republican presidential nomination. >> Laura Bush, Melania Trump speak out on separation of immigrant children, parents at border In an op-ed published Sunday by the Washington Post, former first lady Laura Bush called the Trump administration policy “cruel.” 'I live in a border state,' Bush wrote. 'I appreciate the need to enforce and protect our international boundaries, but this zero-tolerance policy is cruel. It is immoral. And it breaks my heart.' First lady Melania Trump has also criticized the policy, telling CNN in a statement through her spokeswoman that “She believes we need to be a country that follows all laws, but also a country that governs with heart.” Update 12:46 p.m. EDT June 18: President Donald Trump again accused Democrats of obstructing efforts to deal with illegal immigration and the separation of children and parents at the border, telling reporters Monday that “we’re stuck with these horrible laws” because Democrats refuse to sit down with Republicans. There are no laws mandating the separation of children and parents at the border. “We have the worst immigration laws in the entire world,” Trump said. “Nobody has such sad, such bad – and in many cases, such horrible and tough – you see about child separation. You see what’s going on there.” “The United States will not be a migrant camp and it will not be a refugee holding facility,” Trump said. Update 12 p.m. EDT June 18: U.S. Attorney General Jeff Sessions on Monday said authorities don’t want to separate children from their families but that officials have a duty to prosecute people who illegally cross the border. “When we ignore our laws at the border we obviously encourage hundreds of thousands of people a year to likewise ignore our laws and illegally enter our country, creating an enormous burden on our law enforcement, our schools, our hospitals and (our) social programs,” Sessions said Monday during the National Sheriffs’ Association Annual Conference in New Orleans. He framed the issue as a debate over “whether we want to be a country of laws or whether we want to be a country without borders.” “President Trump has said this cannot continue,” Sessions said. “We do not want to separate parents from their children. If we build the wall, if we pass legislation to end the lawlessness, we won’t face these terrible choices. We will have a system where those who need to apply for asylum can do so and those who want to come to this country will apply legally.” Sessions’ arguments echoed those of President Donald Trump, who has blamed Democrats for passing laws that he said led to the separations. There are no laws mandating the separation of children and parents at the border. Homeland Security Secretary Kirstjen Nielsen said earlier Monday that officials will not apologize for enforcing immigration laws. 'We have to do our job,' she said. Original report: President Donald Trump defended his administration’s “zero tolerance” immigration policy on Monday, writing in a series of tweets that children are being used “by the worst criminals on earth” to get into America as critics slammed the policy for separating children from their parents. “Children are being used by some of the worst criminals on earth as a means to enter our country,” Trump wrote. “Has anyone been looking at the Crime taking place south of the border. It is historic, with some countries the most dangerous places in the world. Not going to happen in the U.S.” The president pointed to a rise in crime in Germany as an example of the chaos caused by illegal immigration, writing in a tweet that it was a “big mistake made all over Europe in allowing millions of people in who have so strongly and violently changed their culture.” However, Germany’s internal ministry reported last month that criminal offenses in the country were at their lowest since 1992, according to Reuters. This spring, the Trump administration ordered prosecutors to charge every person illegally crossing the border. Children traveling with the adults have been separated and placed in detention centers, prompting protests nationwide. The president has blamed Democrats for not fixing the law that allows for the separations. “Tell them to start thinking about the people devastated by Crime coming from illegal immigration,” the president wrote. “Change the laws!” Despite his claim that Democrats are at fault for the situation, The Associated Press reported that the Trump administration “put the policy in place and could easily end it.” The Associated Press contributed to this report.