Speaking at a Mississippi rally, he said his opponent “sees people of colour only as votes not as human beings worthy of a better future”.
Mr Trump added that Mrs Clinton and the Democratic party had taken advantage of the African-American community.
Mrs Clinton fired back, saying “he is taking a hate movement mainstream”.
The Democratic presidential nominee called out Mr Trump for questioning the citizenship of President Barack Obama and for failing to disavow former Ku Klux Klan leader David Duke, adding that he was “peddling bigotry and prejudice and paranoia”.
Mr Trump took aim at Mrs Clinton during a campaign stop in Jackson, Mississippi, on Wednesday, where he was joined by Britain’s outgoing UKIP leader Nigel Farage.
Mr Farage, who is viewed as a major force behind the UK’s exit from the EU, told Trump supporters to “get your walking boots on” and begin campaigning.
In recent days, Mr Trump has attempted to court African-Americans after failing to gain support among this key voting bloc.
Only about 2% of black voters say they will vote for the New York businessman, according to current polls.
‘s a standard part of the American political playbook not just to try to exploit your campaign opponent’s weaknesses, but also to diminish his or her perceived strengths.
George W Bush adviser Karl Rove mastered this manoeuvre, best displayed in the 2004 attacks against John Kerry, a decorated veteran, for his Vietnam military service.
So it’s not exactly stunning that Donald Trump is attempting to undermine what a bedrock of Hillary Clinton’s campaign – her support among minority voters, particularly blacks.
The trick, however, is there has to be some appearance of substance behind the charges for them to stick. The reason Kerry was so damaged in 2004 was because the hits came from his fellow veterans and not Mr Bush.
Mr Trump’s calling Mrs Clinton a bigot in a few speeches is likely to bounce off the Democratic nominee if that’s all there is. A wealthy – white – New York billionaire telling blacks how terrible their lives are under Democrats is just not likely fly.
Indeed, attempting to paint the Democratic Party as unconcerned with minority issues, when the party’s rank-and-file is close to a majority minority and its top elected official, Barack Obama, is black is a very tough lift indeed.
Last week, Mr Trump made a direct appeal to black voters during a rally in Michigan, where he told a nearly all-white crowd that African-Americans “are living in poverty” and “their schools are no good”.
In an unscripted plea, he added: “What do you have to lose?”