Megyn Kelly
Fox News star Megyn Kelly wraps it up after a Republican presidential debate in March 2015.Reuters/Jim Young

Donald Trump's one-time nemesis, Megyn Kelly, has joined the list of women accusing Fox News chairman and CEO Roger Ailes of sexual harassment — and Ailes may be heading out the door with a $40m exit payoff.

Fox News star Kelly — who famously grilled Trump during a debate on his use of terms like "dogs" and "fat pigs" to refer to women — told Fox probers investigating sex harassment accusations against Ailes that the CEO had harassed her 10 years ago, New York magazine reported.

Accusations levelled at Ailes began with a lawsuit, first filed in early July by fired anchor Gretchen Carlson, who complained that the 76-year-old CEO pressured her to sleep with him, openly ogled her and commented on her body.

Other women in the past weeks have also spoken up to accuse Ailes of sexually harassing them, although others have also defended him. Ailes called Carlson's suit "defamatory" and said he would vigorously defend himself against the claims.

As for Kelly, Ailes' attorney told the New York Times that his client "has never sexually harassed Megyn Kelly. In fact, he has spent much of the last decade promoting and helping her to achieve the stardom she earned, for which she has repeatedly and publicly thanked him."

When Carlson filed her suit a statement from 21st Century Fox, the network's parent, said the company had "full confidence" in Ailes but that officials were launching an internal investigation into the accusation because "we take these matters seriously."

Now, several media outlets are reporting that Ailes is being forced out by Rupert Murdoch and his sons, James and Lachlan, the three top executives at 21st Century Fox. Sources have told New York magazine that Alies has been given a deadline of the first of August to step down or be fired for cause.

But negotiations are apparently still ongoing and could drag on through the week as both sides bicker over press release language, according to sources. Ailes would reportedly collect around $40m (£31m) under his current contract if he is not fired for cause.

"Roger is at work," 21st Century Fox said in a statement. "The review is ongoing. The only agreement that is in place is his existing employment agreement."

A former Republican Party operative, Ailes built Fox News from nothing 20 years ago to create a hugely profitable media platform for conservative politics in the US. But Kelly has become a force in her own right and is widely regarded as a lynchpin of the future output at Fox, which is becoming increasingly sensitive to its female viewership.