As NBC reels over the shock firing of its biggest star, Matt Lauer, there is increasing pressure on parent company Comcast to launch an independent investigation into what NBC’s top executives knew about Lauer’s treatment of women, and when they knew it.

“This is the largest credibility crisis of any network in broadcast history,” media critic and DePauw University journalism professor Jeff McCall told Fox News.

NBC News Chairman Andy Lack and his deputy, Noah Oppenheim, both have longstanding ties to Lauer going back years and have both spent much of their careers at NBC. Nevertheless, NBC said, “We can say unequivocally, that, prior to Monday night, current NBC News management was never made aware of any complaints about Matt Lauer’s conduct.”

"This is the largest credibility crisis of any network in broadcast history." — Media critic Jeff McCall

This assertion has been met with enormous skepticism by industry observers, amid an avalanche of press accounts saying repeated complaints about Lauer were ignored by executives anxious to please an all-powerful host; and that the “Today” show was a sex-charged “boys club” rife with lewd comments and mistreatment of women.

“It seems that those at the top of the NBC food chain have really dug themselves into a hole. A lot is still unknown, but it could be a lose-lose situation for Lack and Oppenheim. Either they continue their lack of transparency, which only feeds into the narrative that there was complicity among NBC management. Or they reveal the truth, which may also prove complicity among NBC management,” said Mediaite columnist Joey Wulfsohn.

Lack and Oppenheim have stayed largely silent now on three recent scandals about which NBC had promised transparency: Who knew what about Matt Lauer? Why did NBC really spike Ronan Farrow’s story that would have outed Harvey Weinstein as a sexual predator? And why did NBC sit on the infamous "Access Hollywood" tape of Donald Trump and future “Today” co-host Billy Bush making lewd comments about women? On all these issues NBC said they were investigating and would be transparent, and they haven't.

“It seems that those at the top of the NBC food chain have really dug themselves into a hole." — Mediaite columnist Joey Wulfsohn

Now, observers say, the three scandals may well be linked. Could they all be grounded in NBC’s knowledge of, and desire to conceal, the sexual offenses of its most valuable star?

When it comes to Lauer, who was fired this week amid accusations of sexual harassment, University of North Carolina journalism professor and media ethics expert Lois Boynton said from an ethics perspective, “there is a concern about a conflict of interest since the two execs are friends” with Lauer.

Lack is widely known to be a close personal friend of the now-disgraced anchor. It was Lack who promoted Lauer to co-host of “Today” when Lack was president of NBC News in the 1990s. The two men remained good friends during Lack’s time in the wilderness between his NBC stints, and have even vacationed together, according to Vanity Fair. Lack was known as the only NBC executive that Lauer truly respected.

Oppenheim has been in his current job for less than a year but his ties to Lauer run deep. The executive has spent most of his career at NBC, since he graduated from college. This included a multi-year tour of duty as a senior producer at “Today” when Oppenheim worked closely with Lauer in the office and on the road. When Oppenheim returned to NBC in 2015 as the executive in charge of “Today,” he replaced hotheaded exec Jamie Horowitz, who’d been fired by Lauer five weeks into the job after Horowitz sought to make changes to the “Today” talent lineup. “Noah was not allowed to make any decisions related to talent,” said an NBC insider. “Jamie tried.”

NBC insiders said the paralysis of Lack and Oppenheim regarding Lauer was grounded, in part, in their knowledge that Lauer had gone directly to NBC Universal chief Steve Burke when he wanted Horowitz fired, and when, in 2012, he’d objected to a plan that would have put two women executives in charge of “Today.” All this came in the wake of the disastrous firing of the beloved Ann Curry, also done at Lauer’s behest. Of Curry, Lauer was famously reported to have said, “I can’t believe I’m sitting next to this woman.”

The executives’ close relationships with Lauer may also have played a role in their inability to corral his behavior, experts say.

“Oftentimes, we as humans believe that we can act in ways that are independent and we won't be influenced by a relationship such as this,” Boynton said. “Although that may be the case, each of us must also weigh how others perceive the impact of that conflict. In this instance, Mr. Lack and Mr. Oppenheim need to consider a growing perception about whether they can remain independent-minded.”

University of Maryland broadcast journalism professor Mark Feldstein, who has worked at NBC, CNN and ABC, is currently working on a book on media scandals and journalistic malpractice. He’s spent months studying a range of misconduct and how news organizations have handled it over the past generation.

“It varies widely. Some appoint outside independent blue-ribbon commissions to investigate and issue a public report, others investigate internally with or without a public report and some clam up entirely,” Feldstein told Fox News.

Feldstein said that Comcast and NBC have “not offered the public the transparency it deserves,” and questioned why there hasn’t been a detailed public report or a thorough explanation of what occurred and what management knew.

“NBC needs to do better to restore public trust,” he said. “It can't investigate and hold politicians and other corporations accountable for their misconduct if it doesn't openly confront its own.”

Lack left NBC in 2003 but was brought back in 2015, just after the disastrous firing of Horowitz and the embellishments scandal that was consuming Brian Williams, who was also Lack’s personal friend. NBC insiders said that Lauer’s power within NBC increased exponentially under Lack – a largely detached executive -- to the point where the only thing that mattered, especially at “Today,” was keeping Lauer comfortable.

“The executives at NBC seem oblivious to the damage being done to their brand. They just have to come clean and start explaining how the NBC newsroom culture became so corrupt,” media critic Jeff McCall said. “Clearly, NBC can no longer act in the expected press surrogate role for Americans. Even loyal NBC viewers have to be disgusted by what is now being revealed and that the network won't come clean about its problems.”

“NBC needs to do better to restore public trust.” — University of Maryland journalism professor Mark Feldstein

Indeed, with Lauer’s behavior exposed, the spotlight has grown harsher on why Lack and Oppenheim suppressed two other explosive sex harassment stories in the last year.

Oppenheim was at the center the controversial NBC decision a year ago to sit on the explosive “Access Hollywood” tape featuring Donald Trump and Billy Bush making lewd comments about women. At the time NBC was wringing its hands over the tape, Bush was a co-host of the “Today” show, which Oppenheim oversaw.

Eventually the tape was leaked to the Washington Post’s David Fahrenthold, who is Oppenheim’s friend from Harvard University, where Oppenheim and Fahrenthold were editors together at the prestigious Harvard Crimson newspaper. After the tape went public, NBC fired Bush and shortly thereafter promoted Oppenheim to president of news.

Lack and Oppenheim had failed to break, arguably, the biggest story of 2016 when they had it in their hands. History repeated itself in 2017 when they decided against publishing Farrow’s reporting on Weinstein – which is now receiving Pulitzer buzz. Oppenheim publicly took the fall for the decision to spike the story while Lack remained silent.

The Variety reporters who broke the Lauer bombshell, Elizabeth Wagmeister and Ramin Setoodeh, appeared on Fox News’ “Tucker Carlson Tonight” Thursday evening and essentially accused Lack and Oppenheim of lying to cover up knowledge of widespread sexual corruption at 30 Rock.

Setoodeh feels that “it’s a fair question to ask, as a journalist” why Lack and Oppenheim have remained silent and failed to publically clarify what they knew and when they knew it.

“As two reporters who have been covering this story pretty aggressively, we would like to interview either of them,” Setoodeh told Carlson.

Lack initially claimed that a complaint he received on Monday night, that ultimately resulted in Lauer’s firing, was the first complaint regarding his behavior the company has received "in the over 20 years he's been at NBC News." But NBC would later issue a widely noted clarification when it said, in another statement, that "prior to Monday night, current NBC News management was never made aware of any complaints about Matt Lauer’s conduct.”

Setoodeh called it curious that the word “current” was in the network’s statement about which managers knew about Lauer’s sexual misconduct.

Setoodeh explained that NBC staffers have explained to him that the term “current” is being defined in a “very narrow circle” and “there are people who work at the ‘Today’ show, staffers, producers, anchors -- current and previous anchors -- of the ‘Today’ show that were aware there had been complaints about Matt Lauer’s alleged conduct against women.”

Wagmeister said she spoke with members of both the current and former management regimes of the embattled news division and that “it doesn’t matter” which group ignored Lauer’s behavior because “there were multiple claims” against the now-disgraced former anchor.

Wagmeister even echoed a recent tweet by President Trump by saying she has been tipped off about additional men at NBC News who have skeletons in their closets. Also on “Tucker Carlson,” Fox Business Network anchor Melissa Francis said a friend of hers had been sexually assaulted by an NBC executive when she was at the network.

NBC has not contacted the Variety reporters about any internal investigation that the network may, or may not, be launching into the situation, despite the fact that the duo has built up, arguably, the largest collection of damaging information from Lauer’s accusers.

"People are really shocked right now,” Wagmeister said. "They’re waiting for answers.

As NBC loses credibility by the minute, Feldstein thinks that Comcast executives will have to step in.

"Comcast ultimately bears responsibility for what NBC does," he said.

Media watchdog and nwsltr founder Robert D. Buckley told Fox News that the silence from Lack and Oppenheim speaks volumes: "It's simple. NBC went dark once they discovered there was more writing and less winking inside 30 Rock about their own misconduct. It was quietly being chronicled longer than imagined … Remember Lomasney's axiom: 'Never write if you can speak; never speak if you can nod; never nod if you can wink.' Suddenly, NBC realized lots of speaking may begin."

NBC News and Comcast did not respond to separate requests for comment. After this story was published, however, Lack sent an internal memo to staffers that addresses an internal review and greater transparency. Lack and Oppenheim do not appear to take personal responsibility from the portion of the note that has been made public.

"A team of the most experienced NBCUniversal Legal and Human Resources leaders have begun a thorough and timely review of what happened and what we can do to build a culture of greater transparency, openness and respect for each other,” Lack wrote, according to Variety. "At the conclusion of the review we will share what we’ve learned, no matter how painful, and act on it."

"Today" executive producer Don Nash released the following statement: “Never once has any woman or man come to me complaining about Matt Lauer. If they had, I would have gone straight to HR.“