Schiff: Bannon's refusal to answer questions 'unprecedented'

"This was unprecedented in all the interviews that we have done. There have been times where we have taken strong issue with a witness refusing to answer a specific question," the committee's top Democrat explained on "Cuomo Prime Time," mentioning Attorney General Jeff Sessions' refusal to answer a question regarding interference with the Russia investigation.

Bannon, a former White House chief strategist, "refused to answer a broad range of questions" related to his time at the White House and during the transition in his hearing with the Intelligence Committee on Tuesday, Schiff told CNN's Chris Cuomo.

"But here was an entire time period that was essentially made off-limits by the White House," the California Democrat continued. "So we served him with a subpoena during the hearing to convert it from a voluntary appearance to a mandatory one."

Schiff said an attorney for Bannon consulted with the White House after the committee subpoena was served Tuesday and was told his client was still not to answer questions regarding the time during the transition and in the White House.

The House Intelligence Committee is looking into any possible coordination between the Trump campaign and Russia, and is one of several groups investigating the matter. Trump has repeatedly denied any collusion with Russia.