House Judiciary Committee Chairman Jerrold Nadler Jerrold (Jerry) Lewis NadlerSchumer: 'Nothing is off the table' if GOP moves forward with Ginsburg replacement Top Democrats call for DOJ watchdog to probe Barr over possible 2020 election influence House passes bill to protect pregnant workers MORE (D-N.Y.) said Sunday that he wants White House adviser Stephen Miller to testify before Congress over controversial immigration proposals, suggesting Miller is pulling the strings behind the scenes.

“Probably Stephen Miller, who seems to be the boss of everybody on immigration, ought to come before Congress and explain some of these policies," Nadler said on CNN's "State of the Union."

President Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE confirmed Friday a proposal is under consideration to send detained immigrants to “sanctuary cities."

The Washington Post reported it was considered as a way to retaliate against Democrats.

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Miller was reportedly heavily involved in formulating the plan, which was repeatedly rejected by immigration officials.

Nadler has said the plan is "both morally repugnant and probably illegal."

Trump has praised Miller, but denied that he is behind the administration's immigration policy.

“Frankly, there’s only one person that's running it," he said last week. "You know who that is? It's me."

Trump has indicated he will double down on his hard-line positions on immigration by overseeing changes at the Department of Homeland Security that forced the departure of many of the agency’s upper echelon, including Secretary Kirstjen Nielsen Kirstjen Michele NielsenDHS IG won't investigate after watchdog said Wolf, Cuccinelli appointments violated law Appeals court sides with Trump over drawdown of immigrant protections Democrats smell blood with new DHS whistleblower complaint MORE.