Around half of American voters believe Donald Trump is racist despite the US president saying he is the "least racist person in the world", according to a new poll.

The survey was conducted by Quinnipiac University several days after Mr Trump said a group of four congresswomen of colour should "go back" to the countries they came from, even though all four are US citizens.

The survey period, from 25-28 July, also included the day that Mr Trump launched a new attack on black congressman Elijah Cummings.

He called Mr Cummings “a brutal bully” and described his Baltimore district as a “disgusting, rat and rodent infested mess”.

The poll results come as Democrats seeking the party’s nomination for president enter a second round of debates. Nearly all of the 2020 candidates have roundly condemned Mr Trump’s remarks as racist and divisive.

Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam Show all 30 1 /30 Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam Members of the Proud Boys, a fascist group, jeer at anti-Trump protesters outside of the president's 2020 campaign launch in Orlando, Florida Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A supporter dressed as Uncle Sam poses at Uncle Sam Reuters Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A baby blimp rears its head amidst a group of anti-Trump protesters outside the president't campaign launch in Orlando, Florida Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam President Trump addresses supporters at the launch event of his 2020 election campaign in Orlando, Florida Reuters Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam Proud Boys have adopted Fred Perry polo shirts as their uniform and many members have the name of the group tattooed on their arms Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A line of police officers separate opposing groups of protesters outside the launch of President Trump's 2020 campaign launch Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A protester hits a Trump punching bag during a protest outside Trump's 2020 campaign launch in Orlando, Florida Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam Twin Trump supporters pose for a photo at the president's 2020 campaign launch in Orlando, Florida Reuters Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A protester dressed as a caricature of Donald Trump stands outside the president's 2020 campaign launch in Orlando, Florida AP Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A Trump supporter faces off against a protester outside the president's campaign launch in Orlando, Florida AFP/Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A Proud Boy shouts across the police line at anti-Trump protesters outside the president's campaign launch in Orlando, Florida Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A Trump supporter poses for a photo at the president's 2020 campaign launch in Orlando, Florida Reuters Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A Proud Boy jeers at anti-Trump protesters who are separated from the president's supporters by a police line outside the president's campaign launch in Orlando, Florida Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A man dressed as Uncle Sam poses at President Trump's 2020 campaign launch in Orlando, Florida Reuters Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam An anti-Trump protester faces off against a supporter outside the president's campaign launch in Orlando, Florida AFP/Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam Members of the Proud Boys, a fascist group, jeer at anti-Trump protesters outside of the president's 2020 campaign launch Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A child holds a 2020 US "dollar bill" that features Donald Trump's face at the president's 2020 campaign launch EPA Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam Anti-Trump protesters rally outside the president's 2020 campaign launch in Orlando, Florida Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam Anti-Trump protesters rally outside the president's 2020 campaign launch in Orlando, Florida Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam Numerous baby Trump balloons are raised in protests outside of the president's 2020 campaign launch in Orlando, Florida Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A supporter wears a T-shirt depicting Trump as a hero at the president's 2020 campaign launch in Orlando, Florida Reuters Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam President Trump addresses supporters at the launch event of his 2020 election campaign in the Amway Centre in Orlando, Florida AFP/Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam An anti-Trump protester calls for the president to be impeached outside the launch event for his 2020 campaign launch in Orlando, Florida Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam Supporters of Donald Trump face off against protesters outside of the president's 2020 campaign launch in Orlando, Florida AP Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A baby blimp rises behind a group of anti-Trump protesters outside the president's campaign launch in Orlando, Florida AP Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A supporter dressed as Uncle Sam poses at President Trump's 2020 campaign launch in Orlando, Florida AP Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A member of the Proud Boys, a fascist group, holds a sign up outside of the president's 2020 campaign launch in Orlando, Florida AFP/Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam A supporter bears a Trump flag at the president's 2020 campaign launch in Orlando, Florida Reuters Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam Protesters hold baby Trump balloons in the rally outside of the president's 2020 campaign launch in Orlando, Florida Getty Trump 2020 launch: Fascist Proud Boys, baby blimps and Uncle Sam An anti-Trump protester holds a sign accusing the president of being a traitor Getty

The poll found that 51 per cent of voters think Mr Trump is racist while 45 per cent do not.

When separated by party, 86 per cent of Democratic voters classified Mr Trump as racist while 91 per cent of Republicans said he was not.

About 88 per cent of those who said Mr Trump was racist disapprove of the job he is doing as president, while 94 per cent of those who said he was not racist approve of his performance.

Other polls conducted by USA Today/Ipsos, The Economist/YouGov and Fox News in July have shown that between half and two-thirds of Americans believe that telling someone to “go back” is a racist statement and that Mr Trump’s tweets “cross the line”.

Trump supporters chant 'send her back' after president attacks Ilhan Omar

The US president also attacked civil rights leader Reverand Al Sharpton earlier this week. The president denounced Mr Sharpton on Twitter as “a con man” who “Hates Whites & Cops” and doubled down on his attacks against Mr Cummings.

Mr Trump also claimed he is the “least racist person in the world” following his comments attacking politicians of colour and civil rights figures.

The Quinnipac poll found that 41 per cent of survey respondents believe Mr Trump’s immigration policies are motivated by “racist beliefs”, compared with 49 per cent who ascribed them to “a sincere interest in controlling our borders”.