(CNN) The House Oversight Committee Wednesday invited White House senior policy adviser Stephen Miller to testify on the Trump administration's immigration policies on May 1.

Democratic Rep. Elijah Cummings, the chairman of the committee, sent a letter to Miller, the architect behind President Donald Trump's immigration policies, asking him to "appear voluntarily" before the committee. Miller is a prominent voice in the administration's immigration policymaking and has seen his influence rise in recent weeks, leading to a spate of prominent firings and resignations in the Department of Homeland Security. "I am offering you an opportunity to make your case to the Committee and the American people about why you -- and presumably President Trump -- believe it is good policy for the Trump Administration to take the actions it has," Cummings wrote, "including intentionally separating immigrant children from their parents at the border to deter them from coming to the United States, transferring asylum seekers to sanctuary cities as a form of illegal retribution against your political adversaries, and firing top Administration officials who refuse orders to violate the law." Analysis: The secret of Stephen Miller's success Cummings gave Miller until April 24 to inform the committee whether he will agree to testify. CNN previously reported the President told aides in a recent Oval Office meeting that he was putting Miller in charge of all immigration and border issues, according to a person familiar with the meeting. Read More Miller has long channeled Trump's hardline immigration views. Last year, Miller advocated for the administration's "zero tolerance" family separation policy that resulted in children being separated from their parents at the border. He also insisted the White House not waver in its demand for billions of border wall funding before and during the partial government shutdown this winter -- the longest government shutdown in US history, which ended without Trump getting that funding. Most recently, Miller has encouraged Trump to shut down some ports of entry at the US southern border, two administration officials told CNN, even as most of Trump's advisers have warned him of devastating economic consequences in attempts to dissuade him.