George W Bush launches all-out attack on Donald Trump, slams Trump-era politics

George W Bush issued a sharp denunciation of bigotry, white supremacy and falsehoods, in what was seen as a clear rebuke of politics in the age of President Donald Trump.

In a New York speech on Thursday, the two-term former president warned that the coarsening of the national tone and divisive themes are threats to American democracy.

"Bigotry seems emboldened. Our politics seems more vulnerable to conspiracy theories and outright fabrication," Bush said.

Though he did not mention Trump by name, Bush offered an implicit rebuke of the current administration and the controversial politics that emboldened millions of voters who swept Trump to victory last November.

"Bigotry or white supremacy in any form is blasphemy against the American creed," Bush stated, two months after Trump said "both sides" were to blame when a neo-Nazi rally in Virginia turned violent.

He spoke the same day as white supremacist figure Richard Spencer tried to give a speech at a Florida university, but was shouted down.

Argument "turns too easily into animosity," Bush added.

"Disagreement escalates into dehumanization."

Unlike his Democratic successor Barack Obama, the Republican Bush has said very little publicly about Trump or the state of US politics this year.

He declined to endorse Trump's candidacy, and largely stayed above the political fray.

The speech - at the Bush Institute's Spirit of Liberty event - marked a departure from that silence, an expression of concern by a former leader in a unique moment in the nation's history.

"We've seen nationalism distorted into nativism and forgotten the dynamism that immigration has always brought to America," the 71-year-old Bush said, after months of Trump's efforts to rein in immigration and slow the flow of refugees into the United States.