By Brooke Singman, Fox News–

Acting Director of National Intelligence Joseph Maguire, in tense testimony Thursday on Capitol Hill, defended his handling of the explosive whistleblower complaint alleging President Trump pressured the Ukrainian president to investigate the Biden family — while calling the issue “unprecedented.”

Maguire defended himself as “not partisan” and “not political,” reminding the House Intelligence Committee that he served under eight presidents and has taken the oath of office 11 times.

However, he maintained, “I believe that I handled this matter in full compliance with the law at all times.”

Maguire has come under fire from Democrats for initially withholding a copy of the complaint from lawmakers. That standoff was resolved when the complaint was declassified, and released to the public, in advance of the hearing. But Maguire was still pressed for answers from Democratic committee members on why his office did not hand over the complaint at first.

Committee Chairman Adam Schiff, D-Calif., questioned Maguire Thursday over the timeline of his cooperation with the committee.  Maguire said he was not able to release the document at first because of executive privilege concerns and other issues. He also said he is not aware of any instance where such a complaint dealt with such “complicated and sensitive issues.”

“I believe that this matter is unprecedented,” he testified. He also said he does not know the identity of the whistleblower, but said they acted in “good faith.”

The complaint cites “multiple White House officials with direct knowledge of the call” between President Trump and Ukrainian President Volodymyr Zelensky, and accuses Trump of attempting “to pressure the Ukranian leader to take actions to help the President’s 2020 reelection bid.” It also presents allegations that the White House tried to “restrict access” to records of the call.

READ THE WHISTLEBLOWER’S COMPLAINT

The complaint goes on to allege that White House officials said they were “directed” by White House attorneys to remove the transcript of the call from the computer system where they are normally kept. Instead, the transcript was allegedly kept on a different system normally used for classified information.

WHISTLEBLOWER COMPLAINT HAS BEEN DECLASSIFIED AND CONTAINS NO ‘SURPRISES,’ GOP LAWMAKER SAYS

The complaint contains allegations related to Trump’s phone call with Ukrainian President Volodymyr Zelensky in July, when he urged him to investigate former Vice President Joe Biden and his son, Hunter.

Rep. Chris Stewart, R-Utah, a member of the House Intelligence Committee, told Fox News late Wednesday that he had viewed the declassified complaint, and said it didn’t contain any new damning information.

Stewart told “The Ingraham Angle” late Wednesday that he was initially “anxious” before he viewed the complaint, but now is “much more confident than I was this morning that this is going nowhere.”

“There are just no surprises there,” he said.

The White House, on Wednesday, released an unclassified version of the transcript of that highly controversial phone call. The memo, which does not reflect a “verbatim transcript” but is based on “notes and recollections” of those memorializing the call, shows Trump congratulating Zelensky on his election victory before Trump eventually gets to the subject of the Bidens, seeking an investigation of some kind.

Trump first asked Zelensky to do a “favor” and “find out what happened” with the hacking of the DNC server in 2016. He referenced CrowdStrike, a cyber firm used by the DNC to investigate the attacks.

Then, Trump went on to seek assistance in investigating the Bidens.

“The other thing, there’s a lot of talk about Biden’s son, that Biden stopped the prosecution and a lot of people want to find out about that so whatever you can do with the Attorney General would be great,” Trump said. “Biden went around bragging that he stopped the prosecution so if you can look into it…It sounds horrible to me.”

This refers to Joe Biden, while vice president, urging Ukraine to fire its top prosecutor, Viktor Shokin, who was investigating the natural gas firm Burisma Holdings — where Hunter Biden was on the board. Biden has maintained that corruption concerns prompted his intervention.

DEMS DOUBLE DOWN ON IMPEACHMENT AFYER UKRAINE TRANSCRIPT RELEASE

While the transcript shows Trump pressing Ukraine to “look into” the Bidens, it does not show the U.S. president explicitly linking that request to U.S. aid — which had been frozen days earlier, a detail that fueled impeachment calls earlier this week and helped prompt House Speaker Nancy Pelosi to announce a formal impeachment inquiry Tuesday.

Hours after the transcript was released, Trump met with Zelensky on the sidelines of the United Nations General Assembly in New York City. Reporters asked Zelensky about the call with Trump, and whether he felt pressured by the U.S. president, as alleged by the whistleblower—an accusation he denied.

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“I think you read everything. I’m sorry but I don’t want to be involved in democratic elections of the USA,” he said. “We had a good phone call. It was normal, we spoke about many things.”

He added: “I think you read it that nobody pushed me.”

Republicans have also raised concerns about the whistleblower’s possible “political bias,” as the intelligence community inspector general found indications the whistleblower was “in favor of a rival political candidate” of Trump.

Fox News’  Chad Pergram, Gregg Re, Ed Henry, and Jake Gibson contributed to this report.