The Senate's top Democrat says Attorney General Robert Barr has "destroyed the scintilla of credibility he had left" with his testimony before Congress this week.
Schumer says Barr was purposely using phrasing employed by conspiracy theorists and "the president's allies on Fox News." Conservatives have accused the FBI of improperly investigating whether Trump's campaign had inappropriate contacts with Russia.
Schumer says he and fellow Democrats have little faith Barr will be "fair and dispassionate" in deciding what material to withhold when he releases a report by special counsel Robert Mueller.
Mueller investigated Russian involvement in the Trump campaign.
President Donald Trump says he believes Attorney General William Barr was correct in saying that spying did occur on Trump's 2016 presidential campaign.
Trump was asked about Barr's comments during an Oval Office meeting Thursday with South Korean President Moon Jae-in.
Trump says what Barr claimed "was absolutely true."
Trump says he would go a step further and call it "illegal spying," adding "there was spying in my campaign and his answer was a very accurate one."
Barr suggested to Congress the origins of the Russia investigation may have been mishandled, but later said he wasn't sure there had been improper surveillance.
Still, his remarks have given Trump a new avenue to make the assertion that his 2016 campaign was unfairly targeted by the FBI.
Attorney General William Barr says he thinks "spying did occur" against Donald Trump's presidential campaign.
His comments before a Senate panel on Wednesday suggest the origins of the Russia investigation may have been mishandled. Barr's remarks aligned him with the president at a time when his independence is under scrutiny.
Barr did not say what "spying" may have taken place, but he seemed to be alluding to a surveillance warrant the FBI obtained on a Trump aide. He later said he wasn't sure there had been improper surveillance but wanted to make sure proper procedures were followed.
Barr was testifying for a second day at congressional budget hearings that were dominated by questions about special counsel Robert Mueller's Trump-Russia investigation.