Attorney General William Barr's assertion Wednesday that "spying did occur" on President Trump's 2016 campaign has Democrats in an uproar.

Reacting to Barr's testimony, House Judiciary Committee Chairman Jerry Nadler suggested he was misled and demanded answers.

"These comments directly contradict what DOJ previously told us. I’ve asked DOJ to brief us immediately. In the meantime, the AG still owes us the full Mueller report. #ReleaseTheReport," Nadler, D-N.Y., said.

These comments directly contradict what DOJ previously told us. I’ve asked DOJ to brief us immediately. In the meantime, the AG still owes us the full Mueller report. #ReleaseTheReport https://t.co/DFOP5igcnO — (((Rep. Nadler))) (@RepJerryNadler) April 10, 2019

Barr made the stunning declaration during a Senate hearing hours earlier.

[Related: Barr: 'Spying did occur' on Trump campaign]

"I think spying did occur. But the question is whether it was predicated — adequately predicated," Barr testified. "I'm not suggesting it wasn't adequately predicated, but I need to explore that. I think it's my obligation. Congress is usually very concerned about intelligence agencies and law enforcement agencies staying in their proper lane."

"I think spying on a political campaign is a big deal. It's a big deal," Barr added, an apparent reference to GOP allegations that the FBI misled the Foreign Intelligence Surveillance Court to monitor former Trump 2016 campaign foreign policy adviser Carter Page.

Later in the hearing, Barr clarified that he hasn't proven there was any wrongdoing. “I am not saying that improper surveillance occurred, I'm saying that I am concerned about it and looking into it, that's all," he said.

Barr, who is putting a team together to look into surveillance abuse, also said he expects to release a redacted version of special counsel Robert Mueller's final report "hopefully next week."

The Judiciary Committee, ruled by Democrats, voted last week in favor of subpoenaing Barr to turn over the entire Mueller report.

However, Nadler said on Tuesday that his panel, which has oversight over DOJ, will not actually issue a subpoena for Mueller's full report until they see the redacted version provided by Barr.