New York has announced plans to sue the Trump administration over its “zero tolerance” immigration policy, which has resulted in the separation of nearly 2,000 migrant children from their families in recent weeks.

Governor Andrew Cuomo directed three state agencies to sue the federal government on Tuesday, calling the policy a “moral failing and a human tragedy”.

"We will not tolerate the Constitutional rights of children and their parents being violated by our federal government,” Mr Cuomo said in a statement. “New York will act and file suit to end this callous and deliberate attack on immigrant communities, and end this heartless policy once and for all."

Earlier that same day, Mr Cuomo issued an open letter to Vice President Mike Pence, condemning the zero-tolerance policy that the administration enacted in April.

Under the new policy, immigration officials are required to refer anyone caught crossing the border illegally for prosecution – a process that inevitably results in parents being separated from any children they brought with them.

At least 1,995 children were separated from their parents under the new policy between 19 April and 31 May, according to the Department of Homeland Security.

Screaming children heard crying for parents at US detention centre after being separated at border under Trump policy, in distressing audio recording

The White House has claimed it does not have a policy of separating families, and has instead blamed the separations on Congress’s refusal to close loopholes in the immigration system. In a contentious press briefing on Monday, Homeland Security Secretary Kirstjen Nielsen said migrant parents were also to blame.

“Illegal entry is a crime, as determined by Congress,” she told reporters. “By entering our country illegally, often in dangerous circumstances, illegal immigrants are putting their children at risk.”

Human rights groups, religious organisations, and several UN officials have criticised the practice of separating family members at the border, with some likening it to child abuse. Mr Cuomo’s office on Tuesday accused the administration of “callous and inhumane treatment of immigrant families”.

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The governor accused the federal government of violating the constitutional rights of children and families, and of violating the terms of the Flores Settlement Agreement – a 1997 pact that requires the government to quickly release all children who are apprehended crossing the border.

The governor's office said it was aware of more than 70 immigrant children currently living in federal shelters in New York.

Mr Cuomo also announced on Monday that New York would recall its National Guard troops from the US-Mexico border as long as the zero tolerance policy stood. Governors from Colorado and Massachusetts said they would do the same.

“Purposely separating children from their parents is immoral and un-American,” Colorado Governor John Hickenlooper said in a statement.