Rep. Adam Schiff, D-Calif., the top Democrat on the House Intelligence Committee, claims the White House effectively issued a “gag order” on former chief strategist Steve Bannon during his testimony before the panel on Tuesday as they continue their Russia inquiry.

Schiff said that Bannon declined to answer questions regarding his tenure in the White House or his work during the presidential transition.

Although the “gag order” is not a formal invocation of executive privilege by the White House, Schiff told MSNBC host Chris Hayes: “This is the broadest effort to effectively gag a witness we have seen.”

Another Democratic member of the intelligence panel, Rep. Jim Hines of Connecticut, also complained on CNN that Bannon did not answer many of the investigators' questions because of a "very novel theory of executive privilege."

Schiff said that there was no basis for Bannon to decline answering questions from the panel, unless the White House invoked privilege, which hasn’t happened yet.

Bannon’s reticence spurred the committees chairman, Rep. Devin Nunes, R-Calif., to issue a subpoena. Schiff said the subpoena is the first time the committee has had to issue one to a witness who declined to respond to questions per the request of the White House.

Additionally, Mike Conaway, R-Texas, said after the nearly 10-hour interview that the committee would retrieve the answers they were looking for, according to Chad Pergram from Fox News.

"We’re going to get these answers. This witness is not an executive. We have additional questions,” Conaway was quoted as saying.

The panel, along with other congressional committees and special counsel Robert Mueller, are trying to determine whether the Trump campaign colluded with the Kremlin during the 2016 election.

It was reported by the New York Times earlier on Tuesday that Mueller issued a grand jury subpoena to Bannon last week.

White House press secretary Sarah Sanders said Tuesday the White House was not worried about what Bannon would disclose to either Congress or Mueller, but she did not indicate whether the White House instructed Bannon to remain silent for some questions.

"As with all congressional inquiries touching upon the White House, Congress must consult with the White House prior to obtaining confidential material," Sanders said. "This is part of a judicially recognized process that goes back decades. We've been cooperating fully with these ongoing investigations and encourage the committees to work with us to find an appropriate accommodation in order to ensure Congress obtains information necessary to its legitimate interests."

Others close to Trump, including former Trump campaign manager Corey Lewandowski and senior White House aide Rick Dearborn, are expected to testify before the panel later this week.