Donald Trump continues to stand by controversial comments he made about Mexican immigrants as his standings in Republican primary polls improve despite increasing criticism.

The presidential hopeful placed ahead of perceived front-runner Jeb Bush in a new aggregated 'poll of polls' with 13.6 per cent support compared to the former Florida governor's 13.3.

The rise comes as public figures and businesses continue to admonish Trump because of the comments saying that those crossing the border from Mexico illegally were 'rapists'.

Former Republican candidate Mitt Romney told CNN Saturday that the businessman 'made a severe error in saying what he did about Mexican-Americans'.

Trump defended the remarks,and used an interview on Fox and Friends Saturday morning to take a dig at fellow presidential hopeful Marco Rubio.

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Republican presidential candidate Donald Trump defended his comments on immigrants from Mexico on Saturday, when a 'poll of polls' by Fox News said that he was the leading candidate in his party

'Rubio is weak on immigration,' Trump told Fox, while praising the stance of Tea Party favorite Ted Cruz.

He linked policy at the southern US border to crimes, including the San Francisco shooting of 32-year-old Kathryn Steinle by a man who had been deported back to Mexico five times.

'The crime is raging and people don't want to talk about it. And if you talk about it you're a racist,' he said Saturday.

Trump has continued to lose partnerships business after saying in his presidential announcement that migrants from Mexico are 'bringing drugs, they're bringing crime, they're rapists. And some I assume are good people'.

On Saturday NASCAR decided not to hold an event at one of his hotel's in Miami. Univision and NBC have cut ties with his Miss USA and Miss Universe pageants after outrage among Hispanic and Latino groups.

'I'm a little surprised at NASCAR to be honest', Trump said.

While Trump's polling numbers have risen beyond Jeb Bush's, Romney, whose father was born in Mexico, replied that the comments have hurt the Republican party.

He replied 'yes' when asked about the matter, according to CNN.

Former candidate Mitt Romney said that Trump made a 'severe error' in his remarks and that they had hurt the Republican party. Above, from left, Romney, his wife Ann, Mary Pat Christie and candidate Chris Christie

Former New York Governor and Republican candidate George Pataki, who Trump criticized for not doing well in the polls, sent an open letter to those in his party to denounce the Apprentice host.

Some presidential candidates such as Bush have been keen to court the Hispanic vote, speaking Spanish on prominent television appearances and during his announcement speech in a bid to make inroads to the crucial 2016 demographic.

Trump has repeatedly said that he love Mexico despite many saying that his 'rapists' comments were racist against people from the country.

The candidate said that he was being targeted 'from all sides' because he is successful.

He denied that the ordeal was helping him by making him more recognizable. 'This is not good for my brand, I think it's bad for my brand. Maybe I'm leading in polls, but this is certainly not good. I lose customers, lose people,' he said.