US presidential candidate Donald Trump has escalated a fight with Fox News, using the word “bimbo” in a derogatory tweet about host Megyn Kelly after pulling out of a debate only days before the first nominating contest of the 2016 campaign.

On Tuesday, Mr Trump withdrew from the televised encounter, scheduled for Thursday night in Des Moines, Iowa, in irritation at host Fox News for allowing Kelly to moderate after her questioning angered him in a debate last year.

The real estate magnate, who is the frontrunner to win the Republican nomination for the November 8 presidential election, followed up with a thinly veiled insult on Wednesday.

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“I refuse to call Megyn Kelly a bimbo, because that would not be politically correct,” he wrote on Twitter.

“Instead I will only call her a lightweight reporter!”

Mr Trump’s Republican presidential rivals were quick to criticise the former reality TV star, with US senator Ted Cruz of Texas blistering him in a series of tweets and accusing him of “trembling at being questioned by Kelly”.

Another Republican hopeful, Kentucky senator Rand Paul, told Fox News that he welcomed Mr Trump’s absence from the debate stage because it meant “we don’t have to put up with a lot of empty blather and boastfulness and calling people names”.

Mr Trump’s move means the last televised debate before Monday’s Iowa caucuses — which kick off the state-by-state nominating race to choose candidates for the presidential election — will not feature the man who has dominated the Republican race for months and leads many opinion polls.

It was seen as a bold gamble.

‘Poor little Donald’ comes under attack

“It’s a risky move, it’s very high-profile,” former Iowa state party official Craig Robinson said.

“But I’m not sure it will really change anyone’s mind about Trump.”

Mr Trump has been feuding with Fox News since the network put on the first Republican debate in August, in which Kelly asked Mr Trump about his treatment of women, prompting a stream of insults from the candidate and complaints he was not being treated fairly.

It’s not the first time Trump and Ms Kelly have locked horns. Photo: Twitter.

Mr Cruz, Mr Trump’s main rival in Iowa, used the hashtag #DuckingDonald to make fun of him for ducking out of the debate and tweeted a mocked-up picture of Mr Trump’s head on Donald Duck’s body sitting on a pile of money.

Mr Cruz, a conservative and a debating champion in college, challenged Mr Trump to a one-on-one debate.

He tweeted a link to “duckingdonald.com”, which asked visitors to sign a petition in favour of Mr Cruz and Mr Trump having a side debate.

New Jersey Governor Chris Christie, who is also in the Republican race, described Mr Trump’s decision at such a crucial time as “a big mistake” which called into question his ability to be president.

“Any time you get a podium and a microphone and 15-20 million people watching in an election campaign, you should take it,” Mr Christie told Boston Herald Radio.

Another Republican candidate, Florida senator Marco Rubio, said he wanted to focus on keeping the party united in order to beat Hillary Clinton, the former secretary of state, in November if she becomes the Democratic nominee.

“These kinds of theatrics by Ted Cruz and Donald Trump are an entertaining sideshow, but they have nothing to do with defeating Hillary Clinton,” Mr Rubio said.