The best-selling author of a major new book on U.S. intelligence and accused spy Edward Snowden says President-elect Donald Trump is right to call for a major, top-to-bottom review of the intelligence community.

Trump has received heavy criticism in recent weeks for calling into question the credibility of U.S. intelligence agencies in recent months, particularly over whether Russia was responsible for hacking embarrassing emails from the Democratic National Committee and Hillary Clinton’s campaign chairman, John Podesta. Trump now concedes Russia did do the hacking, but says the DNC had weak security and that other countries were hacking as well.

The strained relationship between Trump and the intelligence community has been increasingly obvious in recent weeks. When a briefing on the Russian hacking was delayed on Jan. 3, for instance, Trump tweeted "perhaps more time needed to build a case. Very strange!"

Earlier this month, the Wall Street Journal reported Trump’s transition team is working on a plan to restructure an intelligence community that Trump views as inefficient and politically influenced.

The Central Intelligence Agency and the Direction of National Intelligence office appear to be under the sharpest scrutiny.

The source close to the Trump transition effort told the Journal: "The view from the Trump team is the intelligence world [is] becoming completely politicized. They all need to be slimmed down. The focus will be on restructuring the agencies and how they interact."

Edward Jay Epstein, author of the new book "How America Lost Its Secrets: Edward Snowden, the Man and the Theft," says Trump is on the right track when it comes to challenging the intelligence community’s status quo.

"Trump is certainly correct that we need to go back to square one and look at how our intelligence services are performing," Epstein told Newsmax on Friday. "What’s wrong with them, should they be privatized, what is the security of them — and what are their targets? What are they doing?"

Earlier this week, a thinly sourced, two-page intelligence summary, with salacious content that was unverified and subsequently proven to be erroneous in some respects, was leaked to the media.

Trump dismissed that report as "fake news," and used his Wednesday news conference to suggest the document might have been leaked by "the intelligence agencies."

"I think it was disgraceful," Trump said, "that the intelligence agencies allowed any information that turned out to be so false and fake out.

"I think it’s a disgrace … and that’s something that Nazi Germany would have done and did do. I think it’s a disgrace that information that was false and fake and never happened got released to the public."

Epstein’s new book debuts on Tuesday. His exhaustive research into the Snowden debacle included retracing Snowden’s steps from Tokyo, to Maryland, to Hawaii, to Hong Kong, and finally to Moscow.

U.S. intelligence officials say that in 2013, while Snowden was working as an NSA contractor in Hawaii, he downloaded and copied over 1.5 million secret documents before fleeing to Russia. Revelations from those documents had wide-ranging, global effects.

Beyond the diplomatic turmoil it created, after Snowden’s revelations the terrorist chatter that had provided an early warning of several al-Qaida plots went silent. Analysts believe Snowden’s leaks alerted the terrorists to the scope of U.S. surveillance of emails and the internet.

Epstein contends subsequent terror plots might have been averted, had the Snowden leaks not occurred. He also says the U.S. intelligence apparatus has not yet corrected systemic flaws detailed in his book, which led to the Snowden debacle — considered by some the worst intelligence breech in U.S. history.

"So Trump is right," Epstein says. "We need to re-evaluate the mission of the intelligence services."

On Thursday, the journalist who first published the Snowden revelations, Glenn Greenwald, told Fox News the U.S. intelligence community has been conducting "a lot of subversion" and is now in a state of "open warfare" with the new administration.

Greenwald says during the campaign, CIA officials supported Democratic nominee Hillary Clinton because Trump opposed the agency’s primary policy priority, which was regime change in Syria.

Clinton’s more "confrontational and belligerent posture" toward Moscow was an additional attraction to them, he said.

Greenwald told Fox host Tucker Carlson that liberals and Democrats are "openly calling for and cheering for the intervention of the CIA, the intelligence community, the overall deep state, hoping -- because they failed to do so — that this unelected faction in Washington will undermine and subvert and destroy the legitimacy of Donald Trump’s presidency before he’s even inaugurated.

"I think what you’re seeing is quite dangerous," said Greenwald. "There really is at this point obvious, open warfare."