Stephen Bannon has stepped down as Breitbart News executive chairman, the right-wing news organisation said on its website on Tuesday.
It is the latest fallout from the infamous new book about Donald Trump's presidency. In Michael Wolff's "Fire and Fury", the former chief White House strategist questions the president's mental fitness. A few days ago Bannon expressed "regret" over his remarks.
There has also been a row over remarks he reportedly made about the president's son in the book.
Bannon is said to have described as "treasonous" a meeting Donald Tump Jr held in New York with a Russian lawyer during the 2016 presidential election campaign.
"Steve is a valued part of our legacy, and we will always be grateful for his contributions, and what he has helped us to accomplish," Breitbart Chief Executive Larry Solov said in a statement on the website. It adds that "Bannon and Breitbart will work together on a smooth and orderly transition".
'Fire and Fury' before a fall
Bannon's comments in Wolff's book prompted a bitter falling out between the two former allies.
President Trump responded in a statement last week saying "Stephen Bannon has nothing to do with me or my presidency. When he was fired, he not only lost his job, he lost his mind."
The New York Times reports that Bannon's departure was forced by a onetime financial patron, Rebekah Mercer.
Only five days ago Breitbart's London editor-in-chief Raheem Kassam dismissed the media focus on relations between the president and his former adviser as "tittle-tattle".
Breitbart's readership has soared in recent years, making it the most-read conservative website in the US. Like Bannon himself, it is seen has having played a significant role in Trump's rise to power and has at times been criticised for being a mouthpiece for the president.
Steve Bannon says in the Breitbart statement: "I'm proud of what the Breitbart team has accomplished in so short a period of time in building out a world-class news platform."
Steve Bannon is credited with having been the mastermind behind Trump's election victory. As head of Breitbart News since 2012, he became a champion of the so-called alt-right and made the network a favourite for right-wing Americans, angry at the political mainstream.
Breitbart was not afraid of peddling conspiracy theories and was accused of misogyny and racism, appealing to white supremacists.
Its news chief was looking for a presidential candidate suitable for his populist-nationalist views. Donald Trump was not an automatic choice, apparently, but Bannon was impressed by the tycoon's readiness to step outside accepted political norms - for instance in challenging former President Obama's origins.
The pair shared the same ideology and their approach was typified by the Trump administration's pulling the US out of the Paris climate accord.
However, once in the White House reports quickly spread of a power struggle and tensions between Bannon and the president. Last April Bannon was removed from his role on the influential National Security Council.
Finally, just months into the new tenure, Steve Bannon left the White House in August and back to Breitbart. The criticisms of Trump and his presidency continued nevertheless - culminating in the furore over Wolff's book and Bannon's downfall from the empire he had done so much to build.