Mr Trump's one-time admirers, most from racial minorities, criticised the New York businessman over his divisive rhetoric during his political campaign.

Randal Pinkett, winner of the 2005 fourth season of the show, Kwame Jackson, runner-up from season one, and Tara Dowdell from season three of the show's run, held a joint news conference in Manhattan, with Marshawn Evans Daniels, from season four, appearing via Skype.

Mr Pinkett said: "We are all disappointed and in some ways shocked to see what is being spewed from Donald regarding his views on women, immigrants, and the list goes on.

"We strongly condemn Donald's campaign of sexism, xenophobia, racism, violence, and hate. Donald's proposed policies, or his principles or the apparent lack thereof, make clear that he is not only unqualified to be president of the United States but also that he's a danger to our country and the world." 

Mr Trump hit back, dismissing his former aspiring protégés as "failing wannabes out of hundreds of contestants".
"How quickly they forget. Nobody would know who they are if it weren't for me," he said in a statement. "They just want to get back into the limelight like they had when they were with Trump. Total dishonesty and disloyalty."

Meanwhile, the UN High Commissioner for Human Rights has also taken a swipe at Mr Trump, accusing him of exploiting fear and resorting to bigotry in campaigning that he warned was a "road to violence".

Zeid Ra'ad al Hussein delivered the criticism in a speech at a university in Cleveland, Ohio, where Republicans will gather in July to choose their White House nominee.

Mr Zeid did not refer to Mr Trump by name but he deplored the "frontrunning candidate for president" who declared his support for torture, and took aim at the "multiple candidates" who advocate surveillance and other invasive measures targeting Muslims.

"We have heard these calls to hatred - calls stigmatising and demonising minorities, beginning the validation of violence," he said.

Mr Zeid, a Jordanian diplomat who has been UN rights chief since 2014, said the election campaign had given way to a "full-frontal attack" on America's "hard-won tenets of decency and social cohesion".

"This is also the road to violence," stated Zied, "not perhaps visible - not yet."

Despite the criticisms, Mr Trump has a comfortable advantage in New York opinion polls against rivals Ohio Governor John Kasich and Senator Ted Cruz of Texas. Mr Trump pulled ahead of Mr Cruz and Mr Kasich this week in a Reuters/Ipsos opinion poll.

Among Republicans, 45% support Mr Trump, compared with 29% for Mr Cruz and 21% for Mr Kasich. Democrats Hillary Clinton and Bernie Sanders are tied at 47%.