Mr Bannon, who was senior counsellor to the US president until August, took part in an event organised by the think tank Scotland International Ltd at the five-star Gleneagles Hotel on Friday.
Sir Angus Grossart, who chairs Scotland International, appeared with Mr Bannon, a leading figure in the American right who is accused of promoting white nationalist ideology from within the White House.
Patrick Harvie, the co-convener of the Scottish Green Party, said: “Steve Bannon is a far right extremist, a notorious white nationalist, misogynist and pioneer of hateful ‘fake news’ propaganda.
“It is deeply disturbing that he is now building links with the privileged and connected world of wealthy lobbyists like Angus Grossart.
“If he expects to participate in serious and responsible debate about public policy, Mr Grossart must sever his ties with this dangerous character and others on the new far right.”
Liberal Democrat MP Jamie Stone said public figures who associated with Mr Bannon “should be ashamed”.
“The hateful views he promotes have no place in Scottish and British politics,” Mr Stone said. “Donald Trump’s recent support for the far right in Britain shows we cannot be complacent and need to address this divisive and dangerous agenda head on.”
Labour MSP James Kelly said: “Both the UK and Scottish Government’s should be doing everything they can to ensure merchants of hate are not allowed a market in Britain.
“Bannon’s hateful views have no place in civilised society. Bannon should not be given a platform, however small, to air similar views.”
Mr Grossart is a former vice chairman of the Royal Bank of Scotland and is currently the chairman of fund management company Edinburgh Partners, communications company Charlotte Street Partners, and the body overseeing the refurbishment of the Burrell Collection.
His organisation Scotland International brings together leading business people once a year.
Mr Bannon is reported to have taken part in a Q&A during which participants “didn’t hold back” from challenging his extreme views, according to a source.
During the event, Mr Bannon is understood to have defended the US president’s retweeting of anti-Muslim videos posted by the far-right Britain First group.
During his visit to the UK, Mr Bannon is also reported to have met leading Conservative backbench MP Jacob Rees-Mogg, who told the Andrew Marr Show that a planned state visit by US President should go ahead despite his promotion of anti-Muslim views.
Mr Rees-Mogg dismissed the posts on social media.