Senator Jeff Merkley has obtained compelling evidence that President Trump’s Secretary of Homeland Security lied to the House Judiciary Committee about the administration’s brutal immigration policies, and he is demanding that the FBI open a perjury investigation into Kirstjen Nielsen’s claim that her department “never had a policy for family separation” at the US-Mexican border.

The Oregon Democrat’s bold move to hold a key member of Trump’s cabinet accountable for lying about the administration’s strategies and tactics at the border represents a dramatic development in the ongoing struggle between the executive and legislative branches of a federal government where immigration policy has become a dramatically divisive issue.

“President Trump has shut down the government over a crisis we now know he deliberately created,” says Merkley, who cites a previously secret document created by senior officials with Trump’s Department of Homeland Security and the Department of Justice. “This document shows Trump Administration staffers plotting to create a humanitarian crisis at the border—criminalizing the search for asylum, tearing children from their parents’ arms, and expanding the lock-up of both parents and children.”

The specific accusation that Nielsen lied to Congress stems from an appearance she made before the Judiciary Committee on December 20, 2018, amid a global outcry over ongoing reports of separations at the border.

Nielsen was confronted by US Representative Luis Gutierrez (D-IL).

“It is as if you can’t see the reality of modern immigration or contributions of anyone who came from countries other than Norway or other parts of Europe. It’s as if you and the Trump administration are blind,” he said. “Shame on everybody that separates children and allows them to stay at the other side of the border fearing death, fearing hunger, fearing sickness. Shame on us for wearing our badge of Christianity during Christmas for allowing the secretary to come here and lie.”

Nielsen took umbrage, telling the committee that “calling me a liar is fighting words.”

“I’m not a liar, we’ve never had a policy for family separation,” she declared. That was not the first time Nielsen had issued so bold a denial. On June, 17, 2018, the DHS secretary claimed that “We do not have a policy of separating families at the border. Period.”

But the document that was leaked by a government whistle-blower, and that has now been released to the media by Merkley, reveals that Trump administration officials weighed proposals to target migrant families. An analysis by Merkley’s office concludes that

This document, created by senior Department of Homeland Security and Department of Justice officials, reveals the step-by-step process that the Trump Administration undertook in December 2017 to devise and implement a formal policy of deterring asylum seekers using the threat of family separation. This policy options memo barely mentions violent gangs and drugs, focusing instead on a detailed plan to expand detention by increasing prosecutions of asylum seekers. Despite many statements by the President and senior political appointees to the contrary, this document proves that the administration was in fact intentionally and deliberately planning all along to separate families and create a crisis on the southern U.S. border.

Merkley, who traveled to the border last June and played an essential role in exposing and challenging family separations at the border, now says, “[Secretary Nielsen] and the administration lied. Period. We have proof that the Trump War on Migrant Children was carefully constructed to inflict harm on children and create a humanitarian crisis.”

Based on that proof, Merkley wrote Friday to FBI Director Christopher Wray and formally requested the perjury inquiry.

“The FBI has previously indicated that the Department of Justice requires a formal criminal referral from Congress to initiate an investigation concerning Congressional testimony. I write today to execute such a criminal referral,” wrote the senator. “Compelling new evidence has emerged revealing that high-level Department of Homeland Security officials were secretly and actively developing a new policy and legal framework for separating families as far back as December 2017.”

Merkley concluded: “Despite this fact, while testifying under oath before the House Committee on the Judiciary, Secretary Nielsen stated unequivocally ‘I’m not a liar, we’ve never had a policy for family separation,’ In light of these conflicting facts, the FBI should immediately investigate whether Secretary Nielsen’s statements violate 18 U.S. Code § 1621, 18 U.S.C § 1001, or any other relevant federal statutes that prohibit perjury and false statements to Congress.”

The Trump administration has not taken its duty to cooperate with Congress seriously on many issues. But nowhere has that failure been more pronounced than on the issue of immigration policy.

Merkley is calling them out—not for purposes of partisan positioning but with the moral fury that the actions of Trump, Nielsen, and their associates demands.

“[The] administration was treating children as political pawns, not vulnerable human beings,” says Merkley. “That’s reprehensible. We must end this Trump war on migrant children.”