Top Senate Democrats on Friday demanded that former Attorney General William P. Barr and other Justice Department officials testify before the Judiciary Committee about their extraordinary decision to secretly seize data from the accounts of House Democrats and their aides as they hunted for leaks of classified information.
Senator Chuck Schumer of New York, the majority leader, and Senator Richard J. Durbin of Illinois, the chairman of the judiciary panel, said they were willing to subpoena for testimony Mr. Barr, former Attorney General Jeff Session and others if necessary. They also announced they would “vigorously investigate” the department’s actions and called on Republicans to join them in the inquiry.
“This issue should not be partisan; under the Constitution, Congress is a coequal branch of government and must be protected from an overreaching executive, and we expect that our Republican colleagues will join us in getting to the bottom of this serious matter,” Mr. Schumer and Mr. Durbin said in a statement.
Their demands came as Democrats in both chambers decried the seizures and aggressive investigative tactics, first reported by The New York Times on Thursday, as a gross abuse of power to target another branch of government. They said the pursuit of information on some of President Donald J. Trump’s most visible political adversaries in Congress smacked of dangerous politicization.
So far, no prominent Republicans have joined Democrats in calling for investigations, which could make fact-finding more difficult. The attempt by Mr. Schumer and Mr. Durbin to put pressure on them to stand up for Congress’s prerogatives reflected the fact that to issue subpoenas or compel testimony in an evenly divided Senate, Democrats would need at least some Republican support.
The Times reported that as it hunted for the source of leaks about Trump associates and Russia, the Justice Department had used grand jury subpoenas to compel Apple and one other service provider to hand over data tied to at least a dozen people associated with the House Intelligence Committee beginning in 2017 and 2018. The department then secured a gag order to keep it secret.
Though leak investigations are routine, current and former officials at the Justice Department and in Congress said seizing data on lawmakers is nearly unheard-of outside of corruption investigations. The Times also reported that after an initial round of scrutiny did not turn up evidence tying the intelligence committee to the leaks, Mr. Barr objected to closing out the inquiry and helped revive it.
Investigators gained access to the records of Representative Adam B. Schiff of California, the top Democrat on the committee and now its chairman; Representative Eric Swalwell of California; committee staff; and family members, including one who was a minor.
“I hope every prosecutor who was involved in this is thrown out of the department,” Mr. Swalwell said in an interview on Friday. “It crosses the line of what we do in this country.”
“We have to figure out what and how it happened to determine the extent to which D.O.J. misused its powers under Trump for political purposes,” he continued. “I think it was absolutely a frontal assault on the independence of a coequal branch of government.”
Senator Ron Wyden, Democrat of Oregon and a member of the Intelligence Committee who has been a leading critic of government surveillance, said he planned to introduce legislation trying to crack down on the use of gag orders like the one used on Apple and news organizations, which were also scrutinized in the leak investigation.
“Revelations about the Trump Justice Department’s targeting of journalists and political rivals proves again how surveillance powers can be abused and the need to put strict limits on gag orders that prevent the targets of this spying from learning about it for years,” Mr. Wyden said in a statement.