Ms Harris is the first black and Asian-American vice-president, with Indian and Jamaican-born parents. She attended Howard University, a historically black university, and joined the predominantly black Alpha Kappa Alpha sorority.

She became a member of Congressional Black Caucus after entering the Senate in 2017.

Trump's claims prompted a heated exchange with ABC News' correspondent Rachel Scott, one of the moderators of the Chicago event.

"I respect either one," the Republican said in reference to Harris' racial identity. "But she obviously doesn't because she was Indian all the way and then all of a sudden she made a turn and she became a black person."

White House press secretary Karine Jean-Pierre said no-one "has any right to tell someone who they are, how they identify. That is no-one's right."

"Since when is Donald Trump, with his long and ugly history of racism, the arbiter of Blackness?" congressman Ritchie Torres of New York posted on X. He described Trump as a “relic of a racist past".

The Republican nominee and former president has a history of attacking his opponents on the basis of race.