Republican presidential nominee Mitt Romney speaks at the Colorado Conservative Political Action Committee (CPAC) meeting in Denver (Reuters)

Republican candidate Mitt Romney has backtracked on his claim that almost half the American population are welfare scroungers who would not vote for him and told Fox News that the government "has a responsibility to care for them".

The former Massachusetts governor said his earlier remarks that 47 percent of voters were dependent on benefits and saw themselves as victims were "completely wrong". He was committed, he told Fox, to "helping the 100 per cent" of Americans.

"Clearly, in a campaign with hundreds if not thousands of speeches and question-and-answer sessions, now and then you are going to say something that doesn't come out right," Romney said.

"In this case I said something completely wrong. I absolutely believe, however, that my life has shown that I care about 100 per cent. When I become president, it will be about helping the 100 per cent."

The declaration came just a day after his victorious televised debate against President Barack Obama in Denver, Colorado.

Obama's failure to attack him on the 47 percent remark - a statement that caused Romney so much embarrassment during the electoral campaign - was seen by analysts as a huge missed chance by the president missed to win the debate.

"There are 47 percent of the people who will vote for the president no matter what," Romney had earlier said in off-the-cuff remarks that were secretly taped at a private fundraising event in May and then broadcast online.

"There are 47 percent who are with him, who are dependent upon government, who believe that they are victims, who believe that government has a responsibility to care for them, who believe that they are entitled to health care, to food, to housing, to you name it."

When the video was posted in September, Romney's presidential hopes were almost sunk.

However, political analysts said that his strong performance at Denver put his run for the White House back on track.

His Fox News comments were part of a campaign to get him back in with a chance. His backtracking, however, has been seized on by the Democrat campaign as proof that he cannot be trusted.

"When I got on to the stage, I met this very spirited fellow who claimed to be Mitt Romney," said Obama. "But it couldn't have been Mitt Romney because the real Mitt Romney has been running around the country for the last year promising $5 trillion in tax cuts that favour the wealthy. The fellow on stage last night said he didn't know anything about that.

"Governor Romney may dance around his positions. But if you want to be president, you owe the American people the truth. So here is the truth. Governor Romney cannot pay for his $5 trillion tax plan without blowing up the deficit or sticking it to the middle class. That's the math. We can't afford to go down that road again."

Romney has denied plans to cut taxes by $5tn but experts said that his plan to lower taxes by 20 percent and scrap the alternative minimum and estate taxes would come to the same amount.