Donald Trump has said acting too presidential would be “boring as hell”.

The New York businessman, the frontrunner in the race to become the Republican presidential candidate in the US election, has often been criticised for his tone on the campaign trail.

But at a rally in Superior, Wisconsin, the 69-year-old said his unorthodox style was more entertaining.

“I can be presidential, but if I was presidential I would only have – about 20 per cent of you would be here because it would be boring as hell, I will say,” he told voters at an open airplane hangar, according to Politico.

Mr Trump has come under scrutiny for his language and the insults used as he campaigns to become one of the most powerful leaders in the world.

Marco Rubio, who recently dropped out of the campaign, said: “You have a candidate in Donald Trump who clearly uses language that appeals to anger."

Time reported that he said: "I do think Donald needs to [realise] and take responsibility for the fact that some of the rhetoric he has used could potentially be contributing to this environment that is growing increasingly disturbing for a growing number of Americans.”

Donald Trump's most controversial quotes Show all 14 1 /14 Donald Trump's most controversial quotes Donald Trump's most controversial quotes On Isis: "Some of the candidates, they went in and didn’t know the air conditioner didn’t work and sweated like dogs, and they didn’t know the room was too big because they didn’t have anybody there. How are they going to beat ISIS?" Getty Donald Trump's most controversial quotes On immigration: "I will build a great wall — and nobody builds walls better than me, believe me —and I’ll build them very inexpensively. I will build a great, great wall on our southern border, and I will make Mexico pay for that wall. Mark my words." Reuters Donald Trump's most controversial quotes On Free Trade: "Free trade is terrible. Free trade can be wonderful if you have smart people. But we have stupid people." PAUL J. RICHARDS | AFP | Getty Images Donald Trump's most controversial quotes On Mexicans: "When Mexico sends its people, they’re not sending their best. They’re sending people that have lots of problems. They’re bringing drugs. They’re bringing crime. They’re rapists." Getty Donald Trump's most controversial quotes On China: "I just sold an apartment for $15 million to somebody from China. Am I supposed to dislike them?... I love China. The biggest bank in the world is from China. You know where their United States headquarters is located? In this building, in Trump Tower." Getty Images Donald Trump's most controversial quotes On work: "If you're interested in 'balancing' work and pleasure, stop trying to balance them. Instead make your work more pleasurable." AP Donald Trump's most controversial quotes On success: "What separates the winners from the losers is how a person reacts to each new twist of fate." Donald Trump's most controversial quotes On life: "Everything in life is luck." AFP Donald Trump's most controversial quotes On ambition: "You have to think anyway, so why not think big?" Getty Images Donald Trump's most controversial quotes On his opponents: "Bush is totally in favour of Common Core. I don't see how he can possibly get the nomination. He's weak on immigration. He's in favour of Common Core. How the hell can you vote for this guy? You just can't do it." Reuters Donald Trump's most controversial quotes On Obamacare: "You have to be hit by a tractor, literally, a tractor, to use it, because the deductibles are so high. It's virtually useless. And remember the $5 billion web site?... I have so many web sites, I have them all over the place. I hire people, they do a web site. It costs me $3." Getty Images Donald Trump's most controversial quotes On Barack Obama: "Obama is going to be out playing golf. He might be on one of my courses. I would invite him. I have the best courses in the world. I have one right next to the White House." PA Donald Trump's most controversial quotes On himself: "Love him or hate him, Trump is a man who is certain about what he wants and sets out to get it, no holds barred. Women find his power almost as much of a turn-on as his money." Getty Images Donald Trump's most controversial quotes On America: "The American Dream is dead. But if I get elected president I will bring it back bigger and better and stronger than ever before and we will make America great again." GETTY

Even Mr Trump’s wife, Melania, has urged him to watch his language.

In an interview with CNN’s Anderson Cooper in March, Mrs Trump said her husband would change his tone if he made it to the White House.

But in Wisconsin, Mr Trump asked voters to allow him to be “un-presidential just a little while longer”, while he tries to beat his rivals Ted Cruz and John Kasich to become the Republican nominee.

“We started off with 17 people and now got two left. I call them the leftovers, right? I now have two left and we’re way up on both of them,” he said, Politico reported.

“Let me be un-presidential just for a little while longer,” he added.

The Republican candidate needs 1,237 delegates to win the nominee. So far Mr Trump is miles ahead of his rivals with 737 delegates, according to the latest count by AP. Mr Cruz has 475 delegates, followed by Mr Kasich at 143.

Mr Cruz used Mr Trump’s highly-criticised campaign manner to bolster his own campaign. He told voters in Madison, Wisconsin: “Let’s show the country that this race is not about yelling and screaming and insults.”

The rallies in Wisconsin took place ahead of the presidential primary on Tuesday.