White House Chief Strategist Stephen K. Bannon speaks at the Conservative Political Action Conference (CPAC) in Maryland in February 2017.

Stephen K. Bannon's main financial backer is formally cutting ties with the former Trump adviser.

In a new statement Thursday, billionaire conservative donor Rebekah Mercer said that she has not spoken to Bannon, the former White House chief strategist, in many months and that she continues to support President Trump.

"I support President Trump and the platform upon which he was elected," Mercer said. "My family and I have not communicated with Steve Bannon in many months and have provided no financial support to his political agenda, nor do we support his recent actions and statements."

Mercer almost never speaks publicly, and her statement about her longtime ally represented an extraordinary rebuke. It comes in the wake of new book by journalist Michael Wolff, "Fire and Fury: Inside the Trump White House," which includes incendiary comments by Bannon about the president he helped elect and about Trump's family.

President Trump's former chief strategist Stephen K. Bannon issued an apologetic statement on Jan. 7, as Trump's anger at his unflattering comments in a new book continues. (Jenny Starrs/The Washington Post)

Mercer is arguably the most prominent former Bannon associate to disavow him in the wake of the book's publication. She said she remains committed in her support for Breitbart News, where she holds a minority stake and where Bannon serves as chairman.

People familiar with the conservative news website said discussions have begun at the organization about potentially removing him from the perch that propelled him to them forefront of national conservative politics.

A Bannon spokesperson declined to comment.