In interviews around the publication of a new book, Mr Bannon also predicted that Johnson will become “more populist” over time and said his best option in post-Brexit trade talks with the EU was to go for a “hard out, no deal” outcome.
Bannon is credited with masterminding Trump’s successful bid for the presidency in 2016 after making the Breitbart website which he managed into a rally point for far-right opinion in the US.
He was fired as a White House adviser shortly after the white nationalist rally in Charlottesville in 2017, and has since sought to unify populist forces in the “Judeao-Christian west”. He has previously described Islamophobe Tommy Robinson as the “backbone of Britain” and defended European right-wingers including Marine le Pen in France and Viktor Orban in Hungary.
In an interview with journalist and author Peter Geoghegan, reported in The Observer, Bannon said Mr Cummings was “a brilliant guy”.
“I think Cummings is very smart where he puts his efforts,” said Bannon. “What I like about him is he has the ability to focus on the main things.”
He said that Johnson and Cummings had been “very important” to the drive to get the UK out of the EU, which he backed, but said they were “very late to the party”.
On the talks on the UK’s future relations with the EU, he said: "There is one choice: hard out, no deal. It won't be disruptive.”
He said he expected Mr Johnson to promote “more economic nationalistic tendencies" and predicted that “Boris will adapt his policies to become more populist over time".
Bannon has previously claimed to have advised Johnson on messaging, though the prime minister has rejected the suggestion of close links as a "lefty delusion".
Mr Bannon’s comments were made in interviews linked to Geoghegan’s book Democracy for Sale, but came too late for inclusion.