In the video, published by Mother Jones magazine, the Republican presidential nominee tells a private meeting of big campaign donors that the backers will vote for Obama "no matter what" and that he does not "worry about those people," the Washington Post and other media reported.
"There are 47 percent who are with him, who are dependent upon government, who believe that they are victims, who believe the 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," Romney said."These are people who pay no income tax."
He added that his job "is not to worry about those people. I'll never convince them they should take personal responsibility and care for their lives."
The author of the Mother Jones story said the video was shot apparently surreptitiously at a fundraiser on May 17 at the Boca Raton, Fla., home of Marc Leder, a private equity manager.
The Obama campaign wasted no time seizing on the video.
"It's shocking that a candidate for president of the United States would go behind closed doors and declare to a group of wealthy donors that half the American people view themselves as 'victims,' entitled to handouts, and are unwilling to take 'personal responsibility' for their lives. It's hard to serve as president for all Americans when you've disdainfully written off half the nation," Obama campaign manager Jim Messina said in a statement.
An Obama campaign official, speaking on condition of anonymity, told the Post later that it was "possible" that excerpts from the video will show up in a forthcoming campaign ad.
The Romney campaign, in a statement released later in the day, did not respond directly to the video, but did not challenge its authenticity either.
"Mitt Romney wants to help all Americans struggling in the Obama economy," Romney communications director Gail Gitcho said. "As the governor has made clear all year, he is concerned about the growing number of people who are dependent on the federal government, including the record number of people who are on food stamps, nearly one in six Americans in poverty, and the 23 million Americans who are struggling to find work. Mitt Romney's plan creates 12 million new jobs in four years, grows the economy and moves Americans off of government dependency and into jobs."
Obama faced similar embarrassment when told supporters at a 2008 San Francisco fundraiser that small-town Pennsylvania voters "get bitter, they cling to guns or religion" - a quote that was used against him Monday by Romney's running mate, Paul Ryan, during a campaign event in Des Moines.
The mention of Obama's 2008 remarks - and Ryan's "This Catholic deer hunter is guilty as charged" rejoinder - has been a staple of the GOP vice presidential nominee's stump speech.
In the video, Romney also noted his deficit in the polls among Hispanic voters and joked about his family background. His father, George, was born in Mexico while his American Mormon grandparents lived there. "Had he been born of Mexican parents, I'd have a better shot of winning this."
He added: "I say that jokingly, but it would be helpful to be Latino."
See the video below: