Migrant children are being kept in prison-like conditions with only emergency blankets to keep them warm at the McAllen juvenile detention centre in Texas, footage released by the US government on Tuesday showed.

The facility is run by the US customs and border service. Attorney General Jeff Sessions' new zero-tolerance policy has been blamed for separating families. Under the new rules, all cases of illegal entry are referred for criminal prosecution.

Around 2,000 migrant children have been separated from their parents between mid-April and May, because, unlike their parents, they are not charged with a crime.

U.S. Homeland security secretary, Kirstjen Nielsen, claims Trump administration is simply enforcing the law as photos and audio of children separated from their parents fuel anger.

Homeland security secretary, Kirstjen Nielsen, has rejected criticism of children of illegal immigrants being separated from their parents on the US-Mexico border. Nielsen says her department is 'enforcing the laws as they exist on the books'.

In a rare public statement, Melania Trump, has spoken out against the separation of children from their parents at the US-Mexico border. America's First Lady called on both sides -- Democrats and Republicans -- to come together on immigration reform.

Melania Trump’s spokeswoman, Stephanie Grisham , has said the first lady “hates to see children separated from their families”, in a rare public statement at odds with her husband’s policy of separating children from their parents at the Mexico border.