"Mr. Chairman, I see that your five minutes is up, so I am...", said Whitaker, as there were groans through the hearing room.
In his opening remarks, Whitaker said he was ready to answer questions -but not all of them.
Democrats said they would inquire about Whitaker's past business dealings, too.
Representative Doug Collins of Georgia, the panel's top Republican, said Democrats were staging a "dog-and-pony show" simply "to damage the president".
"Bring your popcorn", he said. And he passed up a chance to break from the president's characterization of the Mueller investigation as a "witch hunt", saying simply, "I think it would be inappropriate for me to comment about an ongoing investigation".
Whitaker testified that he had not spoken with Trump about Mueller and denied interfering with the investigation. If Matt Whitaker had been on trial for the crime of jay-walking or littering, if the Democrats had their way, he would be on death row by now. Mr. Whitaker, you don't run this committee.
"Have you ever been asked to approve any request or action to be taken by the special counsel?"
"It was deeply concerning to me how CNN found out about that", Whitaker said, noting that no other media outlets appeared to be tipped off. The special counsel is honest and "is complying with all regulations".
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Whitaker said he'd read the memo.
"We are pleased to announce that Matthew G. Whitaker, Chief of Staff to Attorney General Jeff Sessions at the Department of Justice, will become our new Acting Attorney General of the United States". He finally pledged to appear if the House dropped its threat of a subpoena.
The dispute emerged amid reports that Democrat and committee chairman Jerrold Nadler was planning to subpoena Mr Whitaker to testify about his interactions with President Donald Trump. The committee and Justice Department eventually agreed he would voluntarily appear on February 8.
The committee's Democrats, including the chairman, Rep. Jerrold Nadler from NY, pushed Whitaker throughout a contentious hearing to explain what he had been told about the Mueller investigation and whether he approved steps taken by Mueller.
The move threw Whitaker's appearance the next morning into uncertainty.
Many of the Democrats have reservations about Barr that hinge on how he will treat Mueller's investigation. Jerry Nadler said he wanted to ask Whitaker if he helped orchestrate Sessions' departure.
"We have obtained new documents showing that you failed to return thousands of dollars that were supposed to be distributed to the victims of World Patent Marketing's alleged fraud, despite your involvement...in handling complaints from individuals of the company's actions", four House committee chairman wrote in a letter to Whitaker dated Thursday. Collins said. "The key difference today is simply that this witness is part of the Trump Administration - and now we're setting a unsafe precedent".