Top Senate Democrats are demanding Attorney General William Barr Bill BarrProsecutor says no charges in Michigan toilet voting display Judge rules Snowden to give up millions from book, speeches The Hill's Morning Report - Sponsored by Facebook - Washington on edge amid SCOTUS vacancy MORE walk back his accusation that the Trump campaign was spied on by the FBI.

Barr sparked a political firestorm earlier Wednesday when he told senators that he believed "spying did occur" during the 2016 election and that he would be reviewing the probe of 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's campaign.

Senate Minority Leader Charles Schumer Chuck SchumerSenate Democrats introduce legislation to probe politicization of pandemic response Schumer interrupted during live briefing by heckler: 'Stop lying to the people' Jacobin editor: Primarying Schumer would force him to fight Trump's SCOTUS nominee MORE (D-N.Y.) accused Barr of "perpetuating conspiracy theories" during his testimony before the Senate Appropriations subcommittee. The hearing was scheduled to discuss the department's budget but ultimately was dominated by questions about special counsel Robert Mueller Robert (Bob) MuellerCNN's Toobin warns McCabe is in 'perilous condition' with emboldened Trump CNN anchor rips Trump over Stone while evoking Clinton-Lynch tarmac meeting The Hill's 12:30 Report: New Hampshire fallout MORE's probe.

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"AG Barr must retract his statement immediately or produce specific evidence to back it up," Schumer said in a tweet.

Sen. Richard Blumenthal (D-Conn.), a member of the Senate Judiciary Committee, added in a statement that Barr had "demanded himself" by "carelessly acting as a mouthpiece for President Trump's conspiracy theories."

“Attorney General Barr must retract his unfounded, irresponsible claim that American law enforcement ‘spied’ on the Trump Campaign. The only spies interfering in the 2016 campaign were Russian ones," Blumenthal said.

He added that Barr's comments have a "real, measurable impact on the lives and safety of our men and women in law enforcement. He owes them a retraction and an apology.”

Barr told senators on Wednesday that he was looking into the FBI's investigation of members of Trump's campaign and that he believes "spying" took place.

"The question is whether it was adequately predicated and I’m not suggesting it wasn’t adequately predicated, but I need to explore that," he said.

Though Barr acknowledged that he did not have "specific evidence" that the FBI behaved improperly that he had "questions."

He later attempted to clarify his initial remarks, saying he is concerned that "improper surveillance" may have taken place during the 2016 election.

"I am not saying that improper surveillance occurred," he said. "I'm saying that I am concerned about it and looking into it. That's all."