George W Bush has maintained a diplomatic front when asked for his views on Donald Trump. However, he reportedly let slip his true opinions during Trump's 20 January inauguration.
New York magazine reports that when Trump finished his dark speech in which he pledged to halt the "American carnage", Bush remarked "that was some weird s***."
A spokesman for Bush declined to comment.
During the rain-swept inauguration, Bush sat near Bill and Hilary Clinton, and Barack and Michelle Obama, and was pictured wrestling with a plastic poncho.
In an official statement ahead of the event, Bush's office said he and his wife Laura were "pleased to be able to witness the peaceful transfer of power - a hallmark of American democracy - and swearing-in of President Trump and Vice President Pence."
Bush did not pledge his support for Trump during the presidential campaign. In the battle for the Republican nomination Trump clashed with Jeb Bush, George W's older brother, taunting him as a "low energy guy" in debates.
In the wake of Trump's election victory, George W Bush, and his father former president George HW Bush, called to offer their congratulations.
In the weeks since Trump took office, George W Bush has offered criticism of the 45th president. When asked about his views about Trump's alleged Russia ties he told NBC: "I think we all need answers."
He also defended the media, whom Trump has attacked as "enemies of the American people", saying: "I consider the media to be indispensable to democracy. We need the media to hold people like me to account."