Those elements were a factor at Fox News, current and former employees have told The Times. The support the company provided Mr. O’Reilly after a prominent sexual harassment case in 2004, which ended with him paying a settlement of about $9 million to a producer, served as a deterrent to other women who might have come forward, they said.

According to Chai Feldblum, a commissioner at the Equal Employment Opportunity Commission who has written extensively on the subject, roughly 70 percent of employees who have experienced harassment do not report it to their employer, typically because they fear retaliation or indifference.

Douglas Wigdor, a lawyer representing three women who are suing Fox News and its corporate parent over racial discrimination from a longtime employee whom the network recently dismissed, said heavy reliance on an anonymous hotline for reporting allegations could be inherently suspect.

Employees tend to come forward when they feel that their company is going to handle their complaints fairly and responsibly, whether or not the hotline is anonymous, Mr. Wigdor said. “Where it’s clear based on prior conduct, messaging, how you treat employees when they come forward to make a complaint — that they’re not going to be retaliated against, that it’s taken seriously, I don’t see a need for a hotline,” Mr. Wigdor said.

(Mr. Wigdor said that none of his three clients, who have collectively worked at Fox and its predecessor for more than 25 years, had any recollection of a hotline at the company. The Wigdor firm also represents two employees of The New York Times in a pending federal lawsuit against The Times, alleging age, race and gender discrimination.)

Other plaintiff’s lawyers said anonymous hotlines are often anything but. “They are usually run by third-party vendors, who assign a number to a case, and ask for a method to get back to you,” Ms. Katz said. “Unsophisticated people will provide the company an email and will frequently become the subject of investigation themselves.”

At Sterling Jewelers, the parent company of Kay Jewelers and Jared, employees who reported allegations of sexual harassment by colleagues to an ostensibly anonymous tip line were sometimes contacted by company officials, according to filings in a class-action case against the company. One claimed she was fired not long after being told by a district manager to “grow some thick skin.”