WASHINGTON >> Three Democratic senators asked a U.S. District Court judge Monday to issue an injunction barring Matthew Whitaker from exercising the powers of head of the Justice Department, arguing that President Donald Trump’s installation of Whitaker as acting attorney general violated the Constitution.

The senators — Richard Blumenthal of Connecticut, Mazie K. Hirono of Hawaii and Sheldon Whitehouse of Rhode Island — sit on the Judiciary Committee, which conducts confirmation hearings for attorney general nominees. They argued that an official who had not been Senate-confirmed could not run the Justice Department, even temporarily.

“Because the Senate has not consented to Mr. Whitaker serving as an officer of the United States, his designation by the president to perform the functions and duties of the attorney general violates the Appointments Clause” of the Constitution, the complaint said.

The lawsuit was the latest effort by critics of Trump’s move, which followed his ousting of Attorney General Jeff Sessions this month, to temporarily install Whitaker in his place as the nation’s top law enforcement official.

Whitaker, whom the White House previously installed as Sessions’ chief of staff, is widely seen as a Trump loyalist. His powers now include supervising Robert Mueller, the special counsel running the investigation into whether Trump’s associates conspired with Russia when it interfered in the 2016 election.

In an interview with Fox News that aired Sunday, Trump claimed that he did not know that Whitaker had criticized the Russia investigation before he designated him acting attorney general. Trump also said he would not stop Whitaker if he decided to limit or curtail the investigation.

Last week, litigants in two pending, unrelated lawsuits against Sessions in his official capacity submitted motions asking judges to declare that by law Deputy Attorney General Rod Rosenstein should be his rightful acting successor and so his name, not Whitaker’s, should be substituted as the defendant in the litigation.