“I have offended not only a lot of people I don’t know, but also those closest to me, including my bandmates and for that I am truly sorry.
“As a result of my actions I am taking time away from the band to examine my blindspots.
“For now, please know that I realise how my endorsements have the potential to be viewed as approvals of hateful, divisive behaviour.
“I apologise, as this was not at all my intention.”
In the book, author, jourtnalist and social media personality Ngo calls the Proud Boys a “pro-Trump fraternity” and refers to left-wing activists as a “marauding gang” on a mission to “destroy the nation-state, America in particular”.
Following the release, Winston tweeted: “Finally had the time to read your important book. You’re a brave man.”
Winston has appeared as banjoist and lead guitarist on all four of Mumford & Sons studio albums to date, including ‘Sigh No More’, ‘Babel’, ‘Wilder Mind’ and 2018’s ‘Delta’.
Multi-instrumentalist Ben Lovett previously predicted the band would still be making music and touring in their 70s.
He said: “I could totally see us doing it in 40 years because it’s going to be just as interesting.
“And I say that because we’ve been doing it for over 10 years now and it’s got more interesting.”