Donald Trump has resumed his attacks on Mitt Romney, saying he might bill him for carpets that were ruined during a fundraiser he held for the failed Republican presidential nominee on a rainy day in 2012.

And he demanded an apology from former Mexican president Vicente Fox for dropping an 'F-bomb' in a TV interview in which he said 'I'm not going to pay for that f***ing wall' that Trump has vowed to build on America's southern border at Mexico's expense.

The rambunctious Friday morning affair in a Detroit suburb came the day after a contentious GOP debate in which Trump pushed back against Romney's complaint that the billionaire front-runner is 'a fraud' and 'a phony.'

'The hatred he has!' Trump told thousands in a giant athletic field house at Macomb Community College.

'The hatred, the jealousy, the hatred. It's hard to believe.'

PAY FOR MY CARPETS! Trump held a fundraiser for Mitt Romney on a rainy day in 2012 and said Friday that he might bill the failed 2012 presidential candidate for replacing 'ruined' carpets in his New York pad

APOLOGIZE: Trump said Vicene Fox, the former president of Mexico, should say sorry for dropping an F-bomb on TV when he blasted the Donald's plan for a Mexico-funded border wall

CONTROVERSY: 'I'm not going to pay for that f***ing wall,' Fox said on February 25

Trump later branded him 'Stupid Romney.'

'I'm telling you. He's a stupid person!' Trump said.

'Stupid Mitt. He is a dumb guy.'

'You guys should like him right?' he asked about the Michigan native, as boos shook the rafters.

'The reason he doesn't like me is that I said "You shouldn't run because you're a choke artist You ran against Obama four years ago. It was a race that should have been an easy win",' he said.

Trump recalled Romney's missteps in the final month of the 2012 campaign.

'He made a fool of himself in the second and third debates. I don't know what happened to him,' he said.

'What the hell did happen? Does anyone know?' he blared. And spinning his finger next to his head in a gesture suggesting that Romney was crazy, he blurted: 'He went –'

'You know the sad part is I really helped the guy,' Trump said.

'I mean, I gave him a lot of money. I raised a lot of money. I had two fundraisers in my apartment. In fact one of them was such a rainy day that it ruined the carpets in my apartment. Everyone's coming in. I had hundreds of people. My carpets were ruined. I think I'm going to send him a bill for new carpet.'

'I hate people that think they're hot stuff and they're nothing,' he sniffed.

'Romney's a bitter man,' Trump said.

'Once a choker, always a choker.'

'STUPID': Trump tried out a new descriptive epithet for Mitt Romney, saying he 'choked' in his 2012 election loss to Barack Obama

'LITTLE MARCO': Sen. Marco Rubio is still in Trump's crosshairs as the all-important March 15 Florida primary approaches

Trump also blasted former Mexican president Vicente Fox for cursing during a February 25 interview on Fusion TV.

'I'm not going to pay for that f***ing wall!' Fox said then. 'He should pay for it. He’s got the money.'

'That was shocking and a disgrace,' Trump said Friday. 'And I think he should apologize to the people of Mexico and to the people of the United States.'

'We are calling on him to apologize!'

Trump also said Fox has softened his position on the border wall.

'What's interesting is that at least now he knows the wall is going up,' he said.

'He didn't say "We're not going to allow a wall." In other words we've come a long way.'

'The thing that bothered me about ex-president Fox is the arrogance,' he said.

'They're used to getting their way, 100 per cent. They're not going to get their way, folks. They're not getting their way.'

The Donald also renewed his attacks on Marco Rubio – 'Little Marco,' as he calls him – the first-term Florida senator who is his main roadblock to collecting the Sunshine State's convention delegates in a March 15 winner-take-all primary election.

RALLY TIME: Trump has two events in Michigan on Friday before jetting off to New Orleans

'You know that in Florida, they hate little Marco Rubio so much because of the fact that he never votes. he never shows up to vote,' Trump said.

Rubio has taken the fight to Trump in the past week, calling him a 'con artist' who is dodging questions about policies he would implement in the Oval Office.

'I'll use a word that he uses,' Trump said Friday. 'He has conned the people of Florida into voting for him, and I'll tell you what, they are angry!

'I don't think he's going to do too well' on the 15th, he said. 'They are angry at him.'

The morning rally – punctuated by a few protests repeated chants of 'Build the wall!' and 'We want Trump!' – is the first of three planned for Friday.

Trump will go next to Cadillac, Michigan and then jet to New Orleans for a dinnertime rally.