NEW YORK (AFP) - White House hopeful Donald Trump may be ahead in the opinion polls, but his hometown of New York has become the latest to shun the tycoon for insulting immigrants and war hero John McCain.

"Donald Trump doesn't represent the views of the people of this city - certainly not of the majority," New York Mayor Bill de Blasio told reporters on Monday.

Asked whether there was a campaign on the Democrat city council to cut any existing contracts with Trump's business empire, de Blasio said he did not want to do business with the billionaire.

On any existing contracts, he said he was "not sure" whether it was possible to break them off.

"We're certainly not looking to do any business with him going forward," he said.

De Blasio called Trump's remarks about McCain, a Republican senator from Arizona and one of the country's most respected politicians, "unacceptable."

"Senator McCain is a war hero by any measure, and he really should apologise for that," he said.

The latest opinion poll on Monday put Trump far into the lead in the race for the 2016 Republican nomination, the favourite at 24 per cent of Republican and Republican-leaning independent voters.

He outpaced his rivals Scott Walker (13 per cent) and Jeb Bush (12 per cent) with the widest lead so far in the campaign, according to the Washington Post-ABC News poll.

The survey was conducted from Thursday to Sunday, and the Post said most of the participants were interviewed before Trump laid into McCain on Saturday.

McCain, a former Republican presidential nominee, was held for five years and tortured as a prisoner during the Vietnam war after his plane was shot down in 1967.

He was decorated for his service.

Trump appears to have lashed out at McCain, exasperated with the senator's criticism of his anti-immigrant stance.

'AIN'T GONNA BE PRETTY'

Trump dismissed his military record by saying that a serviceman who was captured could not be a real hero.

"He's not a war hero," Trump said. "He's a war hero because he was captured. I like people that weren't captured, OK?"

New York's right-wing tabloids, the New York Post and the Daily News, have been merciless in their response.

"G.I. Joke," screamed the Daily News on its front page Tuesday, accusing him of using five deferments and a sore foot to dodge the Vietnam draft.

In an op-ed headlined "Donald ducks the draft," it ridiculed Trump for telling America "he is a man of superlatives - extraordinarily wealthy, wildly successful, the smartest dude in any room anywhere, the toughest on the world stage.

"But now he has to show America the stuff he's really made of. It ain't gonna be pretty." On Sunday, the Post put a caricature of Trump sitting on a raft drifting out to sea on the front page with the headline "Don Voyage" and calling Trump "toast" after his McCain insult.

It is not the first time Trump has been mauled.

He lost deals with a string of collaborators, including NBCUniversal and Macy's, for insulting Mexicans.

As a result, Forbes said it downgraded its valuation of his wealth from US$4.1 billion (S$5.6 billion) to US$4 billion since his campaign launch.

When he announced his campaign in New York in mid-June he lashed out at Mexican immigrants, calling them drug dealers, criminals and rapists.

"When Mexico sends its people, they're not sending their best," he thundered.

"They're bringing drugs. They're bringing crime. They're rapists. And some, I assume, are good people."

Colombian singer Shakira called him a "racist" over the comments.