The leaders of two advocacy groups are calling on Comcast and its board to take a deeper look at the company’s culture in the wake of the sexual harassment allegations leveled against longtime anchor Matt Lauer.

An investigation by NBCUniversal’s legal team last month exonerated NBC News management of any wrongdoing in connection with Lauer’s workplace conduct, though advocacy groups criticized the company’s decision not to have an outside law firm conduct the review.

“There is clearly something wrong with a work environment reluctant to hold high-status employees accountable,” UltraViolet and the National Organization for Women in New York City in an open letter to Comcast Chairman and CEO Brian Roberts published ahead of Comcast’s annual shareholder meeting on June 11.

The report found “no evidence” suggesting that NBC News executives, Today show leaders or human resources staff received any complaints about Lauer’s behavior prior to Nov. 27, but fired him after a woman and her lawyer stepped forward with allegations of sexual impropriety.

“The lack of formal complaints at a company does not necessarily indicate the absence of harassment,” the women’s advocates noted in their open letter. “Often, it means women are being silenced.”

Even as the network conducted its months long internal probe of the news division, The Washington Post and Variety reported sexual harassment allegations against another high-profile NBC News figure, Tom Brokaw. The venerable NBC Nightly News anchor denied the charges, claiming he was “ambushed and then perp walked.”

The advocates called on Comcast and NBC to take proactive steps to develop a safe, equitable workplace, including mandatory anti-harassment training, anonymous climate surveys. They said the network should end overly broad non-disclosure agreements in employment contracts, and mandatory arbitration clauses that prevent people from pursuing individual or collective claims in court.

A Comcast spokesperson couldn’t be reached for comment, however at the time the findings were made public, NBC News Chairman Andrew Lack issued a memo to the staff promising some of the changes the advocates are calling for.

Lack said the news organization would create an outside avenue for raising concerns and an independent team of employee counselors to address complaints while emphasizing confidentiality. He also promised deeper training for managers and monitoring of the workplace culture through confidential, focus-group style assessments.

“We cannot change the past,” Lack wrote, “What we can do is learn from it and try to make it right.”