The Democratic chairman of the House Intelligence Committee is blasting two Justice Department officials for saying the department could ultimately refuse to grant Congress access to documents from special counsel Robert Mueller’s probe, with the top Democrat denouncing those claims as "absolutely insupportable."

Appearing at a forum in Washington, D.C., on Tuesday morning, Rep. Adam Schiff, D-Calif., said he wanted to begin the event by responding directly to an ABC News report the day before – a report that appeared to offer the first full response from inside the Justice Department to claims from Schiff and other Democrats that failing to turn over Mueller's final report or other evidence he uncovered would amount to a "double standard."

"We may have seen a more substantial indication that the Justice Department may take a restrictive view of what it can share with either the Congress or the public," Schiff said of what the two Justice Department officials anonymously told ABC News in the Tuesday report. "Make no mistake, it would be a graphic double standard."

Speaking with ABC News on the condition of anonymity, the two senior Justice Department officials insisted congressional demands for information from the Mueller probe are different than demands for information from other recent, high-profile cases because – among other reasons – no federal law enforcement official has spoken publicly about details of the Mueller probe.

In past cases, such as the FBI investigation of former Secretary of State Hillary Clinton's use of a private email server, public statements by former FBI director James Comey specifically about the investigation undercut the Justice Department's ability to argue that certain investigative materials should remain private, the two Justice Department officials told ABC News.

Schiff rejected that assessment, saying, "This is not something that the department can lay at the feet of James Comey."

What's more, Schiff said, "the public interest in getting a full accounting of what Bob Mueller's been able to produce over the past two years is ... far greater than it was in the email investigation given that [Mueller's probe] goes to whether the president or people around him may be compromised by a foreign power."

In fact, when Republicans were in control of Congress and eventually subpoenaed materials from the Clinton email probe, the Justice Department gave lawmakers access to 880,000 pages of documents.

Then, when Republicans were accusing the Justice Department of abusing its authority to target Trump's inner circle and threatened to hold top officials in contempt of Congress, the department offered lawmakers access to a wide array of documents from the FBI's investigation of Russian meddling in the 2016 presidential campaign, including highly-sensitive materials related to Americans targeted in the probe.

"The necessity of the Justice Department appearing even-handed no matter who controls the congress necessitates provision of [Mueller's] materials," Schiff said, speaking at a breakfast hosted by the Christian Science Monitor.

But the Justice Department officials who spoke with ABC News said that, in Mueller's case, there are still ongoing investigations and prosecutions to protect.

By contrast, when the Justice Department provided Congress with hundreds of thousands of pages related to the Clinton email probe, that investigation was "over and closed," one of the officials said. And when the Justice Department provided Congress with materials related to the FBI's Russia-related probe, the department only shared documents when investigations were finished or when operations couldn't be impacted by the release of documents, according to the officials.

In a letter to Congress at the time, Deputy Attorney General Rod Rosenstein said the "voluminous" production of documents was done "in a manner that does not harm the integrity of any ongoing investigation."

Meanwhile, Rosenstein has recently reiterated – in public – longstanding department policy prohibiting the disclosure of information that could harm people who haven't been charged.

Last year, the Justice Department's inspector general concluded Comey violated that policy when in July 2016 he announced Clinton and her aides shouldn't be charged even though they were "extremely careless" in handling classified information.

Without those public comments, the Justice Department could have withheld documents from Congress on the basis that they reflected internal deliberations, according to the two senior officials who spoke with ABC News anonymously. But "from the get-go we had a very, very weak litigating position because" Comey had in effect waived that privilege, one of the official said.

On Tuesday, Schiff insisted that while the Justice Department "should obviously maintain its investigative interests, that cannot be held as an absolute bar to providing materials to Congress." And, Schiff said, the department has hardly engaged in "an ironclad policy" of refusing to disclose information about uncharged persons.

He cited the Justice Department's ultimate willingness to send Republicans in Congress thousands of text messages exchanged between former FBI agent Peter Strzok and FBI attorney Lisa Page, who both repeatedly criticized Trump in strong terms while they worked on the FBI's Clinton email probe and Russia-related investigation.

Strzok and Page "have not been the subject of indictment," Schiff noted.

Democrats fear that even if Mueller fails to find evidence of criminal wrongdoing, he could find evidence of misconduct that the public might never see.

"People are entitled to know it, and Congress is entitled to know it," the chairman of the House Judiciary Committee, Rep. Jerrold Nadler, D-N.Y., told ABC News last week. "It's our job to hold the president accountable."

Mueller could send his final report to Barr in the coming days. It is not expected to detail the findings of spin-off investigations that Mueller referred to prosecutors around the country to pursue separately.

Barr has publicly promised lawmakers that he will then send his own "report" on Mueller's probe to Congress. It's unclear how extensive that document will be.

Schiff and Nadler have said they will sue the Trump administration for Mueller's evidence if necessary.