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US Attorney General Jeff Sessions has been criticised for citing Bible scripture to back up the Trump administration's immigration policy.

At an event in Indiana, Mr Sessions was defending the practice of separating undocumented immigrant families apprehended at the border.

He quoted the New Testament and said having children does not shield border-crossing migrants from prosecution.

The Bible verse was once used to justify US slavery, said critics.

Mr Sessions said on Thursday: "I would cite you to the Apostle Paul and his clear and wise command in Romans 13, to obey the laws of the government because God has ordained the government for his purposes.

"Our policy that can result in short-term separation of families is not unusual or unjustified."

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White House spokeswoman Sarah Sanders would not comment directly on Mr Sessions' remarks, but added "it's very biblical to enforce the law".

In the House, top Democrat Nancy Pelosi attacked the separations as a "barbaric" policy that "has to stop."

The Trump administration policy is supported by some Republicans, but others have expressed misgivings.

Speaking to reporters on Thursday, House Speaker Paul Ryan, Congress' highest-ranking Republican, was asked if he was comfortable with the tactics.

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"No I am not," he responded. "We believe it should be addressed in immigration legislation.

"We don't want kids to be separated from their parents."

The policy has also provoked disquiet among the conservative evangelical community.

Franklin Graham, son of late reverend Billy Graham and a staunch Trump supporter, said the separation policy was "disgraceful".

"It's terrible to see families ripped apart and I don't support that one bit," Graham told the Christian Broadcasting Network on Tuesday.

The United States Conference of Catholic Bishops also condemned the policy on Wednesday.

"Our government has the discretion in our laws to ensure that young children are not separated from their parents and exposed to irreparable harm and trauma.

"While protecting our borders is important, we can and must do better as a government, and as a society, to find other ways to ensure that safety."

On Twitter, many criticised Mr Sessions' citing of the verse given its historical use to justify slavery.

In 1855, the Richmond Daily Dispatch newspaper wrote that hundreds of passages proved "slavery has the divine sanction", citing Romans 13 as one.

The debate around Romans 13 dates back even further. During the American Revolution, both patriots and those loyal to England invoked Romans 13.

At that time, the arguments centred around whether the verse meant only just rulers were to be obeyed versus upholding existing law and order.

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This week, House Republicans pitched a draft immigration legislation that would end the separation of children and parents at the border.

Under the plan, families would be detained together.

Also in the proposal are provisions to protect 1.8 million Daca 'Dreamers', eliminate the diversity lottery, and add $25bn (£18bn) for border security.

The bill, a compromise between moderates and conservatives, is expected to be voted on next week. So will another, more hardline bill.

President Donald Trump said on Friday he would not sign the compromise bill, despite Republican lawmakers having said he supported it.

His remark sent legislators on Capitol Hill scrambling, but the White House later said the president had misspoken and he would back both measures.