The Trump campaign accuses the Democrat of insulting millions of Americans as she says he is galvanising racists and homophobes.
Hillary Clinton has claimed that half the supporters of her presidential rival Donald Trump belong in a “basket of deplorables” of racists, homophobes, sexists, xenophobes, and Islamophobes.
The Democratic nominee accused Mr Trump of galvanising this “irredeemable” group, saying “he has lifted them up”.
Speaking at an LGBT fundraiser in New York, Mrs Clinton said: “You can put half of Trump’s supporters into what I call the basket of deplorables … the racist, sexist, homophobic, xenophobic, Islamophobic – you name it.
“Unfortunately there are people like that, and he has lifted them up … some of those folks, they are irredeemable, but they are not America.”
The other half, the former US Secretary of State claimed, are individuals desperate for change who felt let down by the government and the economy, who need sympathy.
Her comments were rebuked by Mr Trump’s team, with campaign manager Kellyanne Conway saying the comments were “slander” and had insulted to millions of Americans.
Jason Miller, senior communications adviser to the Republican nominee, said Mrs Clinton’s “truly deplorable” remarks “revealed just how little she thinks of the hard-working men and women of America”.
The media are often prevented from attending Mrs Clinton’s fundraisers, but Friday’s event, which featured a performance from Barbara Streisand, had been open to journalists.
A spokesman for the Democratic candidate, Nick Merrill, suggested that she had been referring to the “alt right” movement – a brand of American political conservatism which is associated with white nationalism.
Mr Merrill said on Twitter: “Obviously not everyone supporting Trump is part of the alt right, but alt right leaders are with Trump.
“And their supporters appear to make up half his crowd, when you observe the tone of his events.”
Those attending the fundraiser on Friday were urged by Mrs Clinton to “stage an intervention” if they had friends considering voting for Mr Trump.
The property tycoon and former Apprentice star was campaigning in Florida on the same day, where he said he would order an attack on Iranian boats if they harassed US Navy ships.
He told a crowded rally in Pensacola that if Iran’s “little boats” circled America’s “beautiful destroyers” during his presidency, “they will be shot out of the water.”
He also accused Mrs Clinton of lacking the temperament to be commander in chief, telling supporters: “Personally, I think she’s an unstable person.”