WASHINGTON (REUTERS) - US presidential hopeful Donald Trump's support among Republicans has dropped 12 points in less than a week, marking the real estate mogul's biggest decline since he vaulted to the top of the field in July, according to a Reuters/Ipsos poll.

Trump was the favourite of 31 per cent of Republicans in a rolling poll in the five days ended Nov 27.

That was down from a peak of 43 per cent registered on Nov . 22.

The dip follows criticism of Trump for comments he made in the aftermath of the Nov 13 Paris attacks that killed 130 people and wounded hundreds more.

Following the attacks, Trump told an NBC News reporter that he would support requiring all Muslims within the United States to be registered to a special database, which his critics have likened to the mandatory registration of Jews in Nazi Germany.

Trump has also been criticised for flailing his arms and distorting his speech as he mocked a New York Times reporter, Serge Kovaleski, who is disabled.

Trump mocked the reporter as he defended his unsubstantiated assertion that during the Sept 11, 2001 attacks on the United States, he watched on television as "thousands and thousands" of people in New Jersey cheered while the World Trade Center fell.

Still, Trump is not the only front-runner to slide in the latest survey.

Retired neurosurgeon Ben Carson has seen his poll numbers drift downward and now trails Trump by more than half, with just 15 per cent of Republicans polled saying they would vote for him in the same Nov 27 poll.

As recently as late October, Carson trailed Trump by only six points.

Following Carson, Florida Senator Marco Rubio and Texas Senator Ted Cruz are tied for third place, with more than 8 per cent each.

Following Rubio and Cruz was former Florida Governor Jeb Bush, with 7 per cent.

The five-day rolling average sample size ranged from 464 to 347 respondents between Nov 22 and Nov 27, with a credibility interval of 5.2 to 6.1 percentage points.