Former Fox News chairman Roger Ailes allegedly offered anchor Megyn Kelly to advance her career in return for sexual favours, according to claims in her upcoming book.

The book, Settle For More, is not published until 15 November and is under embargo, but Radar Online said it obtained a leaked passage.

Ms Kelly wrote that she forcefully rejected Mr Ailes’ advances at Fox.

The section concerning her former boss were reportedly added to the manuscript at a later stage.

"Roger began pushing the limits," she alleged.

"There was a pattern to his behaviour. I would be called into Roger’s office, he would shut the door, and over the next hour or two, he would engage in a kind of cat-and-mouse game with me — veering between obviously inappropriate sexually charged comments (e.g. about the ‘very sexy bras’ I must have and how he’d like to see me in them) and legitimate professional advice."

She said he "crossed a new line" in 2006 when he "grabbed [her] repeatedly” and “kissed [her] on the lips".

"He asked me an ominous question: ‘When is your contract up?’ And then, for the third time, he tried to kiss me."

She said she reported him to a supervisor and the harassment ended after six months. She said she refused to defend him when colleagues accused him of sexual harassment.

Ms Kelly’s book release comes as she is renegotiating her contract with Fox News.

Ms Kelly noticeably stayed silent when the news broke that former Fox anchor Gretchen Carlson, followed by anchor Andrea Tantaros and others, were suing Mr Ailes for sexual harassment.