Vice President Joe Biden told voters in southern Virginia on Tuesday that Republican Mitt Romney wanted to put them "back in chains," sparking outrage from the GOP campaign.

Addressing a crowd that included hundreds of black people, Biden said Romney wants to get rid of new Wall Street regulations Obama signed into law after the 2008 financial collapse.

"Unchain Wall Street," Biden said. "They're going to put y'all back in chains."

Romney's campaign said the comments marked a "new low" for the Obama campaign.

"The comments made by the vice president of the United States are not acceptable in our political discourse and demonstrate yet again that the Obama campaign will say and do anything to win this election," said Andrea Saul, Romney's spokeswoman. "President Obama should tell the American people whether he agrees with Joe Biden's comments."

Obama's campaign stood by Biden, saying the comments were a variation on remarks he makes often about the need to "unshackle" the middle class. The campaign said the metaphor was meant to counter Republican calls to unshackle the private sector from Obama-backed regulations.

Obama deputy campaign manager Stephanie Cutter called the Romney campaign's outrage "hypocritical."

"Let's return to that `substantive' debate Mitt Romney and Paul Ryan promised 72 hours ago, but quickly abandoned," she said in a statement.

The flurry over Biden's remarks underscored what the Obama team knows is a constant risk with the vice president _ that his penchant for speaking off the cuff can sometimes result in inartful or off-color comments.

In a less noticed gaffe Tuesday, he told the crowd he was confident their support would help the Obama-Biden ticket carry North Carolina. Biden was speaking in Virginia at the time.

Still, Obama's campaign sees Biden as one of its most valuable assets. The Scranton, Pa., native has a more natural appeal to working-class voters in battleground states like Ohio and Pennsylvania. He also has willingly embraced the traditional vice presidential attack dog role, often launching the campaign's most vigorous criticisms of Romney, and now Romney's running mate Paul Ryan.